Good morning and welcome to our continued coverage of the unrest in the Middle East.
Syria continues to be the focus of international concern with thousands of people fleeing into Turkey to escape the deadly crackdown on pro-democracy protesters.
Here's a round-up of the latest developments:
•Syrian tanks have sealed off the northern town of Jisr al-Shughour, with pro-democracy activists warning that they expect an all-out assault by government troops. More than 20 people were killed across the northern province of Idlib yesterday.
•Syrian helicopter gunships have fired machine guns to disperse thousands of protesters in the north-western town of Maarat al-Numaan in the first reported use of air power to quell unrest in the three-month-old uprising.
•The US has condemned Syria's "outrageous use of violence" against anti-government protesters. The White House said President Bashar al-Assad's regime was leading Syria down a "dangerous path" and called for "an immediate end to the brutality and violence".
•Syria has warned the United Nations against intervening in its internal affairs. Syrian foreign minister Walid al-Moualem said a European draft resolution condemning the country for its crackdown on anti-government protesters would only embolden "extremists and terrorists".
•Turkish prime minister Recep Tayyip Erdogan has accused Assad of failing to take the violence perpetrated by his troops seriously, warning that the crackdown by Syria's intelligence service was "heading towards a massacre".
The besieged town of Jisr al-Shughour is almost deserted this morning, surrounded by tanks and heavy armour, AP reports:
Syrian state television on Saturday said army units arrested several leaders of the alleged armed groups in the area. About 80% of the population has fled, with more than 4,000 Syrians taking sanctuary across the Turkish frontier.
The town – normally inhabited by 41,000 people – has become a focal point of the Syrian revolution ever since Assad's regime vowed to wreak vengeance on its mostly forsaken inhabitants, who the regime accuses of killing 120 government troops last weekend.
Refugees who crossed the border into Turkey said the chaos had erupted as government forces and police mutinied and joined the local population against the forces loyal to Assad.
But AP reports that, despite the build up of Assad's forces, protests have spread to every major town in the region. In the town of Maaret al-Numan, 25 miles (40km) to the south-east of Jisr al-Shughour, thousands of protesters overwhelmed security forces and torched the courthouse and police station.
The BBC's Owen Bennett Jones spoke to refugees just over the border in Turkey who told him Assad's forces were operating a scorched earth policy in the region, with people being shot in their beds.
An elite army division commanded by Assad's younger brother, Maher, is believed to be responsible for most of yesterday's violence, AP reports:
The decision to mobilise his unit against the most serious threats to the Assad regime could be a sign of concern about the loyalty of regular conscripts.
Reuters has more details about the deployment of Syrian helicopter gunships in the northern town of Maarat al-Numaan.
The helicopters opened fire after security forces on the ground killed five protesters, the Syrian Observatory for Human Rights told the news agency:
"At least five helicopters flew over Maarat al-Numaan and began firing their machine guns to disperse the tens of thousands who marched in the protest," one witness said by telephone.
"People hid in fields, under bridges and in their houses, but the firing continued on the mostly empty streets for hours," said the witness, who gave his name as Nawaf.
This brief clip posted on YouTube appears to show a government helicopter flying over the town.
Syria's state television, in contrast, blamed violence in the area on anti-government groups. It made no mention of attack helicopters but said an ambulance helicopter had come under fire over Maarat from "terrorist armed groups," injuring crew.
The release of a report showing that American firms sold around $200m of arms to Bahrain last year is likely to fuel further criticism of US Middle East policy.
The US government approved the military sales just months before the autocratic regime launched its brutal crackdown against pro-democracy protesters, AP reports.
The state department annual report on global sales of US arms showed that licensed defence sales to Bahrain rose by $112m between 2009 and 2010.
The bulks of the military hardware sold was for aircraft and military electronics. But the US also licensed $760,000 in exports of rifles, shotguns and assault weapons, which raises the possibility that some might have been used against protesters.
The opposition Ugarit News channel and Shaam News Network both continue to post videos of the crackdown on protesters on YouTube.
This clip Ugarit News appears to show Syrian security forces opening fire on protesters in Damascus yesterday who were chanting "Peaceful! Peaceful!"
The UK foreign secretary, William Hague, has issued a statement on the anniversary of the protests about the disputed 2009 Iranian presidential elections, which draws parallels between that uprising and the Arab spring.
Two years ago we saw the Iranian people take to the streets to dispute the results of the 2009 Presidential election and demand representation reflecting the will of the people. They were ultimately denied this, but we all remember the scenes of Iranians pouring onto the streets in peaceful protest to demand their civil and political rights. Two years later we have seen similar demonstrations in Tunisia, Egypt and elsewhere in the Arab World; protests that the Iranian regime now claims to support. This feigned support is all the more disturbing when we consider what has happened in Iran since 2009. There has been a brutal crackdown on all those who freely and peacefully sought to express their views and a concerted attempt to silence any opposition. And now there is plenty of evidence that Iran is exporting these same repressive techniques to its long time ally Syria, as Syria's rulers brutalise their people to cling to power.
It is not in our conscience as a nation to stand by as people are stoned, locked up for defending their rights under their constitution, or beaten on the streets by hired thugs. Two years after people took to the streets to demand reform, I want it to be known that our attention has not been diverted and we will continue to call on Iran to implement its international human rights obligations.
Al-Jazeera has a report from the refugee camps on the southern border of Turkey and Syria where thousands have fled the bloodshed.
In this video a man says how he was shot three times on the way back from a funeral in the besieged town of Jisr al-Shughour by Syrian military intelligence offers:
They were waiting for us - like an ambush. When we arrived at a certain spot they just appeared. The people didn't kill outright, they beat them till they died. We had no guns, no arms, nothing in our hands.
A clip on the Shaam News Network purports to show women in distress after fleeing from the town of Jisr al-Shughour.
One of the women in the video posted on YouTube cries: "They took my children."
AP has more on the situation in the besieged town of Jisr al-Shughour, which has been sealed off by tanks and thousands of Assad's forces.
One local resident said Syrian soldiers and police officers who deserted rather than fire on protesters were now involved in the defence of the town, which is expected to soon face an all-out assault by government forces.
An AP reporter, one of several journalists invited to accompany the northern push by Assad's troops, said they came under fire about a mile outside Jisr al-Shughour today.
The government forces blamed snipers stationed in nearby hills. No casualties were reported.
The Turkish foreign ministry has confirmed that more than 4,000 Syrians have now crossed the border with thousands more expected to follow.
Foreign ministry deputy under-secretary Halit Cevik said 4,300 Syrians had already fled to Turkey with many more nearing the border, AP reports.
"Turkey welcomed a great many number of guests in the past in their times of most dire need. We can do that again," he told the state-run Anatolian news agency.
Witnesses in the border province of Hatay said a tent hospital was being set up at the site of one of the refugee camps. The Radikal newspaper said Turkey would establish a buffer zone if the number of refugees exceed 10,000.
An activist helping to co-ordinate the movement of refugees at the Syrian border said the area had already "turned practically into a buffer zone."
The man, who identified himself only as Abu Fadi, told AP: "Families have taken shelter under the trees and there are 7,000 to 10,000 people here now."
In Libya, Pro-Gaddafi forces are surrounding the town of Zlitan, 160 km east of Tripoli, according to the rebels.
A rebel spokesman said clashes were continuing after anti-government forces seized control of some parts of the town.
"Zlitan is still surrounded by Gaddafi troops and they are threatening the residents to surrender or have their women raped by mercenaries," rebel spokesman Ahmed Bani said, althought it was not possible to independently verify his claim.
Zlitan is one of three towns that are largely government controlled between the rebel-held Misrata and the capital. Were it to fall, it could allow the anti-Gaddafi uprising to spread from Misrata, the biggest rebel outpost in western Libya, to Gaddafi's stronghold in Tripoli, Reuters reports.
The news agency said Gaddafi's forces also shelled the city of Gadamis for the first time overnight. The bombardment of the city, 600km (370 miles) south-west of Tripoli on the Tunisia and Algerian border, has opened up a new front in the five-month civil war.
Libyan rebels have taken control of parts of the western oil port of Zawiya, according to opposition spokesmen.
Zawiya was the closest city to Tripoli to fall into rebel hands but the opposition fighters crushed by pro-Gaddafi forces in March, AP reports.
Guma el-Gamaty, a London-based spokesman for the rebels' national council, said the rebels were in control of a large area on the western side of the city.
A rebel fighter who fled Zawiya at the end of March said "there are clashes inside Zawiya itself."
The rebel, who identified himself only as Kamal, said he had spoken with the fighters who were "back in the city".
The Guardian's Middle East correspondent Martin Chulov says Syrian refugees have told him thousands of people are hiding in the hills between the besieged town of Jisr al-Shughour and the Turkish border.
Refugees in Antakya say thousands hiding in hills between jisr al-shughour & border. Too terrified to move. Helicopters hunting them. #syrialess than a minute ago via txt 
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Martin Chulov
martinchulov
Posting on Twitter, Chulov also reports that another man who fled the town last night said Assad's forces were operating a "scorched earth policy".
Reuters has more about the situation Zawiyah where Libyan government forces are engaged in fierce fighting with rebels.
"The situation is very bad in Zawiyah. There's been fierce fighting since the morning between the Gaddafi forces and the rebels," said a resident, who gave only his first name, Mohammed.
Chulov also reports claims that Iranian security forces might be assisting Assad's regime in the crackdown on the popular uprising.
Amother wounded refugee spoke 2day of capturing bearded man who spoke no arabic in jisr al-shughour. Iranian boots on ground?less than a minute ago via txt Favorite Retweet ReplyMartin Chulov
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There have been several reports this week that the Basij militia, an Iranian volunteer force of Islamic government loyalists, have taken part in the oppression of Syrian protesters.
More than 10,000 demonstrators have joined Bahrain's first public rally in months, AP reports.
The demonstration organised by the country's main Shia political party took place in an area north-west of the capital Manama. Police helicopters flew overhead but government security forces stayed back from the crowds.
Meanwhile the opposition criticised the appointment of the speaker of the country's parliament to lead a national dialogue after the crackdown on democracy protests.
Khalifa al-Dhahrani, speaker of the Council of Representatives, said he hoped to bring "all parties concerned with matters of the state" into the dialogue, Reuters reports.
But Shia opposition group Wefaq said the king or the crown prince should be the regime's chief negotiator.
"The real dialogue that needs to take place must be between the king or the crown prince and the opposition because what we are discussing is a pivotal issue of difference between the ruling family and the people," said Khalil al-Marzooq.
"We call for the crown prince to lead these talks... to pull this country out of the bottle neck which it is stuck in."
We're closing this live blog now. But coverage of the Middle East uprisings will continue on the website tomorrow and in the Observer.
In the meantime, here's a round-up of today's main developments:
•The besieged town of Jisr al-Shughour in northern Syria has been sealed off by tanks and thousands of Assad's forces. Around 80% of its 43,000 inhabitants have fled.
•At least 41,000 Syrian refugees have fled across the border into Turkey, according to the Turkish foreign ministry.
•In Libya, pro-Gaddafi forces are surrounding the town of Zlitan, 160 km east of Tripoli.
•Fierce clashes have broken out between pro-Gaddafi troops and rebels in the town of Zawiyah, shutting the coastal highway that links the capital Tripoli with Tunisia.
•In Bahrain, more than 10,000 demonstrators attended the country's first public rally against the regime in months.
