The sectarian standoff between Bahrain's Shia majority and its Sunni elite deteriorated further on Tuesday when the king declared martial law and security forces clashed violently with protesters throughout the capital, Manama.
At least three people were killed in fighting between the civilian protesters and government-backed security forces that included Saudi soldiers invited into the kingdom on Sunday.
Hospitals were again teeming with wounded demonstrators in scenes reminiscent of earlier clashes in February, that severely tested the legitimacy of the US-backed government. A hospital source said two men, one Bahraini and the other Bangladeshi, were killed in clashes. State television said a Bahraini policeman was also killed, denying media reports that a Saudi soldier had been shot dead.
Soldiers were active in numerous areas that had been flashpoints in past clashes. Doctors and medical staff reported that troops had taken over a medical centre in the Sitra area and, in some cases, prevented them from tending to casualties. Doctors in the medical centre claimed they were being prevented from leaving by troops stationed outside.
"They are shooting at us, they are shooting," one doctor told the Guardian. "Get help, get the international community to help."
Up to 200 people were reported to have been treated at some point during the day, which is being seen as the start of a new phase in the increasingly bitter clashes that are steadily gaining a regional dimension in the Gulf. Bahrain withdrew its ambassador to Tehran in protest at a warning from the Iranian foreign minister, Ali Akbar Salehi, to the kingdom not to harm demonstrators, almost all of whom are Shias. Meanwhile, the Gulf states and Saudi Arabia said they felt obliged to intervene, claiming that continuing unrest in Bahrain could threaten them.
In a further sign of the crisis's broader reach, Hezbollah in Lebanon said that military intervention against a popular uprising would complicate Bahrain's already fragile social dynamic. Saudi Arabia's restive Shia minority was also thought to be angered by the intervention, as is the Shia majority government in Iraq.
Villages throughout Manama stationed militiamen at entrances and crossroads in attempts to keep security forces away. However, they were unarmed, outnumbered and unable to stop soldiers taking over neighbourhoods to search for demonstrators.
Earlier, Bahrain's monarch, King Hamad bin Issa al-Khalifa, had declared a state of emergency for three months and given the military broad powers to quell the uprising, which has been steadily eroding the authority of the 200-year-old monarchy.
"The commander-in-chief of the Bahrain defence force has been mandated to take the measures and procedures necessary to preserve the safety of the nation and its people," the government statement said. It added that "other forces" may also be invited to Bahrain.
The economic toll on the kingdom has been rapidly mounting as demonstrators have occupied a landmark in central Manama, Pearl roundabout, and marched on government buildings demanding changes. This year's Formula One grand prix in Bahrain has been postponed and is unlikely to be rescheduled as the tiny state's reputation as a safe financial hub and a haven for tourism has taken a heavy hit.
The UK has closed its embassy in Manama, while the EU and the US have said there is "no military solution" to the crisis. The US maintains its Fifth Fleet in Manama's port and has significant intelligence interests in the kingdom.
The foreign secretary, William Hague, said: "We're extremely concerned about the escalation of the situation in Bahrain, in particular the decision by the government of Bahrain to declare a state of emergency."
The US claims the intervention of Gulf nations' soldiers is not an invasion. However, it appears to be caught between its recent advocacy of democracy over stability in the Middle East, and the reality that its own strategic interests in the region could unwind if it continues to push for change.
"The Americans were with us last month and now they're not," said Dr Ala'a from the Salmaniya medical centre, which treated scores of wounded during the day. "What does that say about them? Democracy is fine when it suits their interests, but when it's not they will happily subject us to the savagery of people like this." Ala'a said several of the injured treated had gunshot wounds. The two men killed in the clashes had also been shot, she said.
Photographs and videos of dead and injured circulating supported her claims.
"With our blood and our souls we will fight the mercenaries," a crowd chanted in the car park of the hospital, which has been a rallying point for the uprising for the past two months.
A key issue of the demonstrators is that many members of the Bahrain security forces are from Gulf – Sunni – states in the region and they have been given nationality by the regime. Bahrain's Shias make up 70% of the country, but do not have access to many establishment roles, such as senior positions in the army or police.