Bahrain's army deployed across Manama on Thursday and vowed "strict measures" to restore order after a police raid on anti-regime protesters killed three, wounded nearly 200 and enraged the opposition.
Protesters gathered during the day outside a hospital where the wounded are being treated to chant anti-regime slogans, while the largest Shiite opposition bloc said it was quitting Parliament and called on the government to resign.
Concerned that events in Bahrain could destabilise the entire region, foreign ministers of the Gulf monarchies were to hold an emergency meeting later on Thursday in Manama, Bahrain's foreign ministry said.
The protesters' demands have two main objectives: force the ruling Sunni monarchy to give up its control over top government posts and all critical decisions, and address grievances held by the country's majority Shiites who claim they face systematic discrimination.
Witnesses said riot police stormed through Pearl Square, the epicentre of pro-democracy protests that have shaken the Gulf island state, in the early hours of Thursday firing hollow-point bullets, rubber bullets and tear gas, sending hundreds of protesters fleeing.
"The health ministry has counted three dead and around 195 wounded," Health Minister Faisal al-Hamr was quoted by the official BNA news agency as saying.
Opposition members and witnesses said the police raid was launched without warning at around 3am (midnight GMT).
"They attacked the square, where hundreds of people were spending the night in tents," said 37-year-old Fadel Ahmad.
At the city's main Salmaniya hospital, medical staff were overwhelmed as ambulances and private cars were still ferrying in the injured hours after the assault began.
Witnesses said dozens of armoured military vehicles were parked near Pearl Square as the military warned of "strict measures" to restore security in Bahrain, where clashes this week have left a total of six people dead.
Bahrain's defence forces will "take all strict and preventive measures to restore security and public order," a defence ministry spokesperson said, urging people to "refrain from gathering in vital areas."