Hello, this is Warren Murray opening our latest live blog coverage of Libya, where clashes are continuing despite the regime declaring a ceasefire under threat of a no-fly zone backed by the UN.
Overnight there were patchy reports of shelling and explosions around Benghazi and the situation ramped up significantly with confirmation that a fighter plane has been shot down over the city.
Here's a summary of the latest developments:
• A fighter plane has been shot down over Benghazi. Video and photos showed the jet flying over the city, then bursting into flames and plunging into the suburbs, with the pilot apparently ejecting.
• Loud explosions have been heard in the opposition stronghold, with those on the ground saying government forces have been shelling the rebels. Rebels said they had been forced to pull back as Libyan jets bombed the road to Benghazi airport and the city's outskirts.
• In response the Libyan regime has denied any involvement, saying its entire air force has been grounded and it is respecting its self-imposed ceasefire.
• The next stage of the international response is to be co-ordinated at an emergency conference in Paris within a few hours. David Cameron, Nicolas Sarkozy, Hillary Clinton and Arab leaders are among those gathering to give final approval for a no-fly zone. There is a sense that jets will be streaking out to Libya as soon as the group gives the nod.
We'll have all the latest news as it develops.
This is David Batty, I'll be taking over the live blog until Saturday evening.
AP has more on the fighter plane shot down in Benghazi. One of its reporters saw the plane "go down in flames and heard the sound of artillery and crackling gunfire in the distance":
The fighting galvanized the people of Benghazi, with young men collecting bottles to make Molotov cocktails. Some residents dragged bed frames and metal scraps into the streets to make roadblocks.
"Where is France, where is Nato?" cried a 50-year-old woman in Benghazi. "It's too late."
Government spokesman Ibrahim Musa denied that a government plane had gone down. He also denied government forces shelled any Libyan towns on Saturday, saying the rebels are the ones breaking the cease fire by attacking military forces."Our armed forces continue to retreat and hide, but the rebels keep shelling us and provoking us," Musa told AP.
Gaddafi's propaganda war continues on Saturday with the Libyan state news agency claiming his forces are under attack by "al-Qaida gangs" near Benghazi.
The Jana news agency report, which contradicts other media reports showing pro-Gaddafi forces attacking the rebel stronghold, states: "Al-Qaida gangs are attacking units of the armed forces which are stationary west of Benghazi."
It is worth noting that pro-Gaddafi officials describe all the rebels as belonging to al-Qaida.
My colleague Chris McGreal has just called in from Benghazi about the plane shot down over the city:
"Some of the rebels say it's their plane. It might have been their only plane that was shot down by Gaddafi's forces."
He has been down to the frontline of the fighting in the south west of the city where Gaddafi's forces have seized control of the university.
We'll have more details on this soon.
Here's an interview with Chris McGreal about the fighting in Benghazi, including the shooting down of a fighter jet, which "the rebels now concede it was their only plane".
He adds there is currently "sporadic but fairly intense fighting" in the south west of the city where Gaddafi's forces have broken through. There are also reports of fighting in the north of the city.
Gaddafi has again warned against military intervention in Libya, describing any such act as "clear aggression", Reuters reports.
"This is injustice, this is clear aggression. You will regret it if you take a step towards interfering in our internal affairs," Gaddafi wrote in a letter to France, Britain and the United Nations, according to a spokesman for his regime.
The spokesman, Mussa Ibrahim, also said Gaddafi had warned the US in a separate letter that he and all Libyans were "prepared to die" to defend the country.
AP has more details of the letters Gaddafi has sent to the UN and the US.
In the letter to France, the UK and the UN secretary general, he claimed the UN resolution authorising international military intervention in Libya was "invalid" and they would "regret" enforcing it.
"Libya is not for you, Libya is for the Libyans," he wrote.
In the other letter, sent to US President Barack Obama, Gaddafi defended his decision to attack rebel cities: "If you found them taking over American cities by the force of arms, tell me what you would do."
A rebel leader in Benghazi has appealed to the international community to stop the bombardment of the city by Gaddafi's forces.
Mustafa Abdul Jalil told Al Jazeera television:
"Now there is a bombardment by artillery and rockets on all districts of Benghazi. There will be a catastrophe if the international community does not implement the resolutions of the UN security council.
"We appeal to the international community, to the all the free world, to stop this tyranny from exterminating civilians."
Another rebel spokesman, Khalid al-Sayeh, told Reuters that Gaddafi's forces had "entered Benghazi from the west":
"Where are the Western powers? They said they could strike within hours."
Pro-Gaddafi forces have fired four or five artillery shells at the Misrata but remain on the outskirts of the rebel-held city, a resident has told Reuters:
"They [Gaddafi's forces] bombed the town with four or five artillery shells in the early hours today. The situation is relatively calm now. But they are still on the outskirts of the town, and water to Misrata is still cut off."
A doctor in the city, Libya's third largest, earlier told AP that it came under sustained assault well after the announcement of a cease-fire by Gaddafi's regime.
The doctor said Gaddafi's snipers were on rooftops and his forces were searching homes for rebels. He had counted 25 dead since Friday morning:
"The shelling is continuing, and they are using flashlights to perform surgery. We don't have anesthetic to put our patients down."
More on the situation in Benghazi where Gaddafi's troops have entered the city and are fighting rebel forces.
One witness told Reuters they saw a blast near the rebel national council building that was barricaded by concrete blocks.
Six 4x4 pick-ups mounted with machine guns were moved to the Benghazi seafront. But the relatively light arms of rebel forces have proved a poor match for Gaddafi's heavy firepower.
Standing next to his Benghazi home, Hassan Marouf, 58, said: "Europe and America have sold us out. We have been hearing bombing all night, and they have been doing nothing. Why?"
"We have no one to help us but God. Us men are not afraid to die, but I have women and children inside and they are crying and in tears. help us," he said.
Pro-Gaddafi snipers have killed two people in Misrata, Reuters reports.
A resident, called Saadoun, told the news agency:
"We have two people dead this morning ... because there are snipers on some houses and they are shooting people, they are shooting whoever they see."
Journalist Rob Crilly, who is in Benghazi for the Daily Telegraph, has been tweeting about the plane shot down over Benghazi. Like our correspondent Chris McGreal, he has been told it was a rebel fighter jet:
"Rebels telling us they think the plane shot down was a rebel plane - fog of war. we only saw one. No-one able to ID it. Consensus was that it wasn't a mig - possibly a mirage."
The Libyan rebels' leader movement has denied a Libyan state television report that the former interior minister who defected to the rebels has returned to Gaddafi's government.
Libyan state television said Abdel Fattah Younes al Abidi had been reappointed as interior minister and showed footage of him being greeted by Gaddafi. It was not clear when the footage was filmed.
Abidi was appointed to head the rebel movement's armed forces on March 15. Mustafa Abdel-Jalil, head of the rebel council, told Al Jazeera that Abidi was still leading the rebel forces.
Thousands of civilians are fleeing Benghazi as Gaddafi's forces penetrate further into the rebel stronghold, Reuters reports.
Hundreds of cars full of civilians headed out of Benghazi on Saturday and drove to rebel-held areas of Libya further east, a Reuters correspondent said.
"Do we have to wait till he [Gaddafi] kills us all before the [world] acts. We are very disappointed," said Adel Mansoura, an air traffic controller fleeing Benghazi with his family and voicing the same concerns as many in the east at the failure of the West to take swift UN-authorised military action.
"When we heard the UN resolution, we were very happy and thought we had our freedom but now we have been left on our own to the killers," he said at a petrol station where dozens of other cars queued for fuel as they fled.
Others making the exodus expressed the same dismay as they fled east in the direction of the Egyptian border where many Libyans have already crossed for fear of attacks.
Morocco, Qatar, Jordan and the United Arab Emirates are the Arab nations attending the emergency summit on Libya in Paris, AFP reports.
AP reports that Gaddafi's forces and the rebels are fighting in the city's university.
Abdel-Hafez, a 49-year-old Benghazi resident, told the news agency that fighting had broken out on the university campus in the south of the city, with government tanks and ground troops advancing into the area.
AP also reports that young men in the city are collecting bottles to make gasoline bombs, while other residents have dragged bed frames and metal scraps into the streets to make roadblocks in a bid to halt the advance of Gaddafi's forces
The pro-Gaddafi state-run Jana news agency has reported that crowds of Libyans are converging on targets which France is expected to attack. This raises concern that Gaddafi could use civilians as human shields around military targets.
The Libyan oil minister, Shukri Ghanem, has urged Western firms which abandoned operations in the country at the outbreak of unrest last month to return.
He warned that contracts may otherwise be handed over to companies from countries such as China and India, which did not back military action.
The statement appears to be a veiled warning to the international community of what is at stake if military intervention goes ahead.
Al Jazeera TV has broadcast images of rebel tanks in the streets of Benghazi waving the flag of the revolution after Gaddafi forces pulled back.
The news channel earlier reported that the cease fire announced by Gaddafi's regime was never mentioned on national television and appears to have only been aimed at the international media and governments.
This video shows the rebels' only fighter jet being downed over the Libyan city of Benghazi on Saturday, and shelling of the rebel-held Misurata by Gaddafi's forces, despite the announcement of a ceasefire.
Labour leader Ed Miliband has given his backing to international action to stop Gaddafi "murdering his own people".
In a speech to the Scottish Labour conference in Glasgow, Miliband said:
"To stand by, to do nothing, would be totally wrong. We know in our hearts and our heads when we see Gaddafi murdering his own people it is right to take this action."
He also paid tribute to the "brave men and women who may be asked to serve in Libya", including those from RAF bases in Scotland.
Al Jazeera reports that 26 dead and more than 40 wounded are in Jala hospital in Benghazi after the city was bombarded by pro-Gaddafi forces.
The anti-Gaddafi Libya February 17 blog is flagging up a livestreaming video from someone called Mohammed, who is driving around Benghazi, reporting on the damage to the city via his video phone.
Pro-Gaddafi forces have been driven out of Benghazi by anti-government troops, Reuters reports.
Nasr al-Kikili, a lawyer who works for the rebel media centre in Benghazi, said:
"We revolutionaries have taken control of four tanks inside Benghazi. Rebel forces have pushed Gaddafi's forces out of Benghazi and are combing the western gate area for Gaddafi's troops."
We're still waiting for an announcement from Paris where Western and Arab leaders are holding an emergency summit over the crisis in Libya.
French officials have said that they expect military action to enforce the UN resolution against Gaddafi's regime could begin within hours after the meeting.
British prime minister David Cameron, French president Nicholas Sarkozy, and US secretary of state Hillary Clinton held talks before the before the start of the summit at the Elysee Palace.
They are understood to have viewed footage of this morning's events in Benghazi, including the downing of the jet, and were said to be "monitoring the situation on the ground very closely", PA reports.
British deputy prime minister Nick Clegg chaired a meeting of the government's Cobra emergency planning committee in Downing Street.
In his regular weekly video message released in Washington, President Obama said: "We will work with our partners in the region to protect innocent civilians in Libya and hold the Gaddafi regime to account."
Here's a video of his earlier warning to Gaddafi to honour the UN-backed ceasefire and no-fly zone or face military action.
A Benghazi resident has told Sky News how Gaddafi's forces shelled houses and cars in residential areas of the city:
"We have been under continuous bombing since about six o'clock this morning. It was non-stop. Civilians are being attacked in Benghazi."
Here's a lunchtime round-up of the latest developments in Libya:
•Fighting has continued in and around the rebel-held cities of Benghazi and Misrata, despite Gaddafi's government claiming it would honour a UN-backed ceasefire.
•Rebel leaders have appealed to the international community to stop the pro-Gaddafi bombardment. Thousands of civilians have fled Benghazi, travelling towards the Egyptian border.
•A fighter plane has been shot down over Benghazi. Although it was initially thought to belong to Gaddafi's forces, rebels in the city have said it was their only jet.
•Western and Arab leaders are meeting at an emergency summit in Paris to agree on what action to take to enforce a UN resolution allowing air strikes on Libya.
•Gaddafi has warned Western leaders they would regret enforcing the UN resolution, which he described as invalid.
Here's the Guardian's latest story on the crisis in Libya, which focuses on the battles between pro-Gaddafi forces and rebels in and around Benghazi.
Misrata residents have said that government snipers are shooting people from rooftops and the hospital can not operate on the wounded because it has no anaesthetic.
Misrata, about 200km east of Tripoli, is the last big rebel stronghold in the west of the country and people living there say Gaddafi forces are still trying to retake it despite a ceasefire.
People said there was some shelling in the city this morning and that the city was facing a humanitarian crisis because water supplies were cut for a third day.
A Misrata resident called Saadoun told Reuters:
"I am telling you, we are scared and we are alone. We have two people dead this morning, not because of the shelling but because there are snipers on some houses and they are shooting people, they are shooting whoever they see... We are all scared here, the people of Misrata are scared. We feel a humanitarian crisis is coming."
French TV station BFM reports that French fighter jets are over Benghazi enforcing the no-fly zone. AFP also reports that several French fighter jets overflew "all Libyan territory" on reconnaissance missions.
The Guardian has been sent videos of fighting in Misrata, purportedly showing the bombing of civilian targets by pro-Gaddafi forces on Friday.
This video appears to show armed rebels, some in trucks fitted with machine guns, shouting as plumes of smoke appear on the horizon following what sounds like artillery fire. Please note we cannot independently verify this footage.
AFP has more about the jet fighter shot down earlier on Saturday over Benghazi.
The news agency reports that rebel forces confirmed the pilot was one of their supporters.
The plane, at a former Libyan air force jet, crashed as it tried to attack pro-Gaddafi troops on the outskirts of the city.
French President Sarkozy is due to make a statement on Libya "shortly" as the emergency summit in Paris wraps up, the BBC reports.
British, French and Canadian fighter planes could carry out the first strikes against Gaddafi's forces later on Saturday, ahead of wider Nato action, the Dutch prime minister, Mark Rutte, has said after the Paris summit.
French president Nicolas Sarkozy greets British prime minister David Cameron at the Elysee palace summit to discuss implementing the UN security council resolution on Libya. Photograph: Ian Langsdon/EPA
Sarkozy has confirmed that French fighter planes are already enforcing the no-fly zone over Libya, particularly Benghazi.
Speaking at a press conference after the emergency Paris summit, he said: "As of now our aircraft are preventing [Gaddafi's] planes from attacking the town."
Speaking after the Paris summit, British prime minister David Cameron said Gaddafi had broken the ceasefire and the time for action had come.
A Dassault's Rafale French fighter plane Photograph: Pierre Verdy/AFP/Getty Images
More details of Sarkozy's comments following the Paris summit on the crisis in Libya.
The French president said that "as of now" his country's air force is ready to attack the tanks and planes loyal to Gaddafi to defend the people of Benghazi.
Our airforce will oppose any aggression by Colonel Gaddafi against the population of Benghazi.
As of now, our aircraft are preventing planes from attacking the town. As of now, other French aircraft are ready to intervene against tanks, armoured vehicles threatening unarmed civilians.
The president added that, despite a ceasefire announcement on Friday, Gaddafi had flouted the UN's demand for an immediate end to violence against his people.
In Libya, a peaceful civilian population that is seeking only to be able to choose its own destiny has found itself in mortal danger. It's our duty to respond to their appeal.
Today we are intervening in Libya under the UN mandate with our partners and notably our Arab partners. We are doing it to protect the civilian population from the murderous madness of a regime that in killing its own people has lost all legitimacy.
There is still time for Colonel Gaddafi to avoid the worst, by acting without delay and without reservations in accordance with all the demands of the international community. The door of international diplomacy will open again the moment attacks end.
Here's more of David Cameron's comments after the Paris summit. The British prime minister said that action to defend the Libyan people against Gaddafi's forces "must take place urgently".
Asked if military action was about to begin, Cameron said:
Colonel Gaddafi has made this happen. He has lied to the international community, he has promised a ceasefire, he has broken that ceasefire.
He continues to brutalise his own people and so the time for action has come. It needs to be urgent, we have to enforce the will of the United Nations and we cannot allow the slaughter of civilians to continue.
What is absolutely clear is that Gaddafi has broken his word, he has broken confidence and continues to slaughter his own civilians.
This has to stop, we have to make him stop and make him face the consequences. I think action must take place urgently.
He acknowledged there would be "dangers and difficulties" involved in the operation, but said action was necessary:
There will be unforseeable consequences of taking action, but better taken action than risk the consequences of inaction.
PA reports that two US F-15 Strike Eagle ground attack jets have taken off from US Air Force base at Lakenheath, near Bury St Edmunds, Suffolk, in England.
US planes took off from the same base in 1986 to bomb Libya.
Italian fighter planes have begun a surveillance mission over Libya, Al Arabiya television channel reports.
French Mirage and Rafale fighters are flying over Benghazi and could strike at Gaddafi's tanks, AP quotes an official from Sarkozy's government as saying.
The communique on enforcing the UN resolution agreed by world leaders at the Paris summit reads:
"Our commitment is for the long term: we will not let Colonel Gaddafi and his regime go on defying the will of the international community and scorning that of his people.
"We will continue our aid to the Libyans so that they can rebuild their country, fully respecting Libya's sovereignty and territorial integrity."
A Canadian CF-18A fighter plane prepares to land at the Birgi Nato airbase in Trapani in the southern Italian island of Sicily on 19 March. Photograph: Alessandro Bianchi/Reuters
Contradicting earlier media reports, Italian prime minister Silvio Berlusconi has said his country is currently only providing bases for the military operation against Libya.
Italian news agency ANSA also quoted Berlusconi as saying Italian jet could air join raid if necessary.
Reuters has more on the build-up of Western forces that could be involved in military action to enforce the UN resolution.
The news agency reports that six Danish F-16 fighter jets at the US air base in Sicily, and American F-18s and Canadian CF-18 Hornets are already in the region.
Danish air force spokesman Lars Skjoldan said the six their F-16s that arrived at the US air base at Sigonella, Sicily on Saturday would be ready for operation in Libya by Sunday.
Canada has committed six CF-18 fighter jets to help enforce the no-fly zone, and early Saturday Canadian aircraft landed at the Prestwick Airport in Glasgow, Scotland to refuel and left, an airport spokesman said.
Andrew MacDougall, a spokesman for Canadian prime minister Stephen Harper, said it would take two days to prepare for any mission.
Italy has offered the use of seven military bases to help enforce the no-fly zone over Libya
Witnesses reported Saturday that five American F-18s, two C-17s and a C-130 cargo plane landed Saturday at the US air base at Aviano in northern Italy, which is home to the 31st Fighter Wing.
Here's a summary of events this afternoon
• Military action has begun against Libya, with French jets seen in the skies over Benghazi. Six Danish F-16s have arrived at the US air base at Sigonella, Sicily on Saturday and will be ready for operation Sunday. Canada has committed six CF-18 jets,and Canadian aircraft landed at the Prestwick Airport south-west of Glasgow, Scotland to refuel.
• International leaders have been meeting in Paris. The British prime minister said that action to defend the Libyan people against Gaddafi's forces "must take place urgently". He said: "Colonel Gaddafi has made this happen. He has lied to the international community, he has promised a ceasefire, he has broken that ceasefire."
• A fighter plane has been shot down over Benghazi. Although it was initially thought to belong to Gaddafi's forces, rebels in the city have said it was their only jet.
• Fighting has continued in and around the rebel-held cities of Benghazi and Misrata, despite Gaddafi's government claiming it would honour a UN-backed ceasefire. Gaddafi's forces entered south-west Benghazi, but rebels claimed to have beaten them back.
I've just spoken to my colleague Chris McGreal in Benghazi where rebel forces have pushed back Gaddafi's forces from the city after intense fighting in which scores of civilians and fighters were killed.
He says there is a real wariness among the rebels that Gaddafi's forces were able to penetrate the city's defences and take over areas of what has been the main rebel stronghold in Libya since the uprising began.
Many residents also feel let down by the West because it delayed taking military action after the UN resolution was passed. They believe they will not be safe until Gaddafi is deposed or dead.
Our correspondent in Rome, Tom Kington, has more on the involvement of other nations' air forces.
Spanish and Belgium fighter aircraft are due to arrive in Italy before taking part in operations over Libya, a source in Italy said on Saturday. Spain would likely send F-18 aircraft, Belgium F-16s.
Six Danish F-16 fighters have landed at the Sigonella airbase in Sicily. Sigonella is home to Italian and US surveillance aircraft. The first of four unmanned US Global Hawk aircraft to be deployed at Sigonella arrived in September.
Witnesses reported that five American F-18s, two C-17s and a C-130 cargo plane had landed at the Aviano air base in northern Italy which used by the US military.
The Italian air force has dispatched Tornado and Eurofighter aircraft to its Trapani air base in western Sicily in readiness, although Italian prime minister Silvio Berlusconi said on Saturday that Italy was supplying bases only for now.
Libya Alhurra TV has announced that its founder Mohammed Al Nabbous, also known as Mo, has been shot dead by Gaddafi troops in Benghazi.
We posted a link to his livestreaming video earlier on Saturday.
Barack Obama has said the international community is resolved to protect the people of Libya.
Speaking during a visit to Brazil, the US president said:
Our consensus was strong, and our resolve is clear. The people of Libya must be protected. In the absence of an immediate end to the violence against civilians, our coalition is prepared to act and act with urgency.
US secretary of state, Hillary Clinton, has said that while the US will not deploy ground troops in Libya "there should be no mistaking our commitment to this effort".
She told a press conference after the Paris summit that the US would help its European and Canadian allies and Arab partners stop Gaddafi from attacking the Libyan people.
Colonel Gaddafi continues to defy the world and his attacks on civilians go on... As President Obama has said, we have every reason to fear that left unchecked, Gaddafi will commit unspeakable atrocities. We all recognise that further delay will only put more civilians at risk.
Let me be clear about the position of the US. We will support an international coalition as it takes all necessary measures to enforce the terms of Resolution 1973. French planes were in the air as we were meeting and there will be other actions to follow. There is no doubt that we will begin to enforce the resolution.
A French fighter jet has fired on a Libyan military vehicle in the first reported strike in the international campaign to enforce a no-fly zone, AP reports.
French defence ministry spokesman Thierry Burkhard said the strike was reported around 1645 GMT Saturday. Burkhard says the target was confirmed as a military vehicle, but it was not clear what kind.
As many as 20 French planes are involved in operations to enforce the no-fly zone over Libya, PA reports.
Canadian prime minister Stephen Harper said "extensive" allied aerial operations will start soon, involving his own country's planes, along with a naval blockade of Libya.
The parameters of our mission are clear, they are wide-ranging and they do not include on-the-ground action.
It is our belief that if Mr Gaddafi loses the capacity to enforce his will through vastly superior armed forces, he simply will not be able to sustain his grip on the country.
This is Matt Wells taking over from David Batty. The French aircraft carrier Charles de Gaulle is being moved to international waters off the coast of Libya, according to Le Monde.
The French aircraft carrier Charles de Gaulle. Photograph: Franck Prevel/Reuters
It will leave the French port of Toulon on Sunday and will be in place within 48 hours.
French media is reporting that Benghazi rebels admit they shot down their own plane today.
Al-Jazeera is reporting that French war planes have destroyed four Libyan tanks in air strikes to the south west of Benghazi.
The death has been announced of Mohammad Nabbous, described as the "face of citizen journalism in Libya". Nabbous was apparently shot dead by Gaddafi forces in Benghazi on Saturday.
Andy Carvin, social media strategist at NPR, said on Twitter: "Mohammad Nabbous was my primary contact in Libya, and the face of Libyan citizen journalism. And now he's dead, killed in a firefight."
. Here's a fuller story.
The International Committee of the Red Cross has called on all sides in the Libya crisis to spare civilians and respect international humanitarian law.
Our corespondent Chris McGreal has spent the day in Benghazi and has filed this report. It shows that residents were frustrated about the time it took for international forces to muster jets to enforce the UN no-fly zone.
"Where are the air strikes? Why is the west waiting until it is too late?" asked Khalid el-Samad, a 27-year-old chemical engineer, who shook his finger in fury. "Sarkozy said it. Obama said it. Gaddafi must stop. So why do they do nothing? Is it just talk while we die?"
Here's the latest, full roundup on the situation today. This live blog is now ending, although we will update it if there are any big, urgent developments. Otherwise stay tuned to guardian.co.uk or our Libya page.
• Western planes led strikes against Muammar Gaddafi's military as world leaders ordered the biggest intervention in the Arab world since allied forces invaded Iraq in 2003. "The patience of the international community finally ran out," write our correspondents in our latest full news story.
• Rebels in Benghazi pleaded for air strikes to begin as Gaddafi's forces advanced on the eastern city of Benghazi. Chris McGreal, reporting from the city, said residents "reeled in shock as the rebels initially fell back and then fought hard to contain the assault while artillery fire rocked parts of the city for much of the day".
• In Tripoli, Libyans loyal to Gaddafi scorned the UN resolution and blamed al-Qaida for the rebellion in their country. Ian Black, our Middle East editor, who is in the Libyan capital, says in this report that "patriotic songs boomed out from giant loudspeakers mounted in the centre of Tripoli's Green Square."
Hello, this is Luke Heeley. We are re-opening the live blog as events unfold in Libya.
The Pentagon has issued a statement that Operation Odyssey Dawn is under way, with the launching of 110 Tomahawk missiles by US and British ships and submarines at strategic targets in Libya.
Details of the statement have been published on the US Department of Defence's website:
Coalition forces launched "Operation Odyssey Dawn" today to enforce U.N. Security Council Resolution 1973 to protect the Libyan people from the country's ruler.
The goal of the military coalition is to prevent further attacks by regime forces on Libyan citizens, officials said, adding that the coalition also wants to degrade the ability of Moammar Gadhafi's regime to resist a no-fly zone being implemented.
U.S. military forces are on the leading edge of the coalition operation, taking out Libya's integrated air and missile defense system, Defense Department officials said. The ordnance is aimed at radars and anti-aircraft sites around the capital of Tripoli and other facilities along the Mediterranean coast.
Operation Odyssey Dawn is commanded by U.S. Navy Adm. Samuel J. Locklear aboard the command ship USS Mount Whitney. The Mount Whitney joins 24 other ships from Italy, Canada, the United Kingdom and France in launching the operation.
Cruise missiles from U.S. submarines and frigates began the attack on the anti-aircraft system. A senior defense official speaking on background said the attacks will "open up the environment so we could enforce the no-fly zone from east to west throughout Libya."
In addition to the cruise missiles, the United States will provide command and control and logistics. American airmen and sailors also will launch electronic attacks against the systems.
The United Kingdom, France, Italy and Canada already have announced that they are part of the coalition. Officials expect Arab countries will publicly announce their participation soon.
Al-Jazeera television reports that Libya's rebel military council has been co-ordinating with the international coalition that launched air strikes against areas where Gaddafi's forces were present. It also said Western forces had bombarded a military college near the city of Misrata in west Libya where it said Gaddafi's forces were based.
Al-Jazeera also says Libyan authorities have detained a team of its journalists in western Libya. The network says in a statement that the four correspondents are Tunisian, Mauritanian, Norwegian and British. They were reporting from Libya for several days. It says: "Libyan authorities will be held responsible for the safety, security and well-being of the team who are being held in Tripoli."
Libyan state television reports that the "crusader enemy", a reference to Western forces, has bombarded civilian areas of several cities, including the capital Tripoli, Gaddafi's hometown Sirte and the rebel stronghold of Benghazi.
David Cameron has given a statement following a meeting of the British government's Cobra emergency committee:
Tonight, British forces are in action over Libya. They are part of an international coalition that has come together to enforce the will of the United Nations and to support the Libyan people.
We have all seen the appalling brutality that Colonel Gaddafi has meted out against his own people. And far from introducing the ceasefire he spoke about, he has actually stepped up the attacks and the brutality that we can all see.
So what we are doing is necessary, it is legal, and it is right.
It is necessary because, with others, we should be trying to prevent him using his military against his own people.
It is legal, because we have the backing of the United Nations Security Council and also of the Arab League and many others.
And it is right because we believe we should not stand aside while this dictator murders his own people.
Tonight, of course our thoughts should be with those in our armed services who are putting their lives at risk in order to save the lives of others. They are the bravest of the brave.
But I believe we should all be confident that what we are doing is in a just cause and in our nation's interest.
We are now closing this blog – but our live coverage continues in a new live blog here. Comments will close in 30 minutes.