Bahrain's military deployed armoured vehicles in the centre of Manama and vowed to restore order Thursday after a violent police raid on anti-regime protesters left four people dead and scores wounded.
Enraged by the brutal crackdown, the largest Shiite opposition bloc said it was planning to quit parliament while angry protesters gathered outside a hospital where victims are being treated to chant anti-regime slogans.
Riot police stormed through Pearl Square, the epicenter of pro-democracy protests that have shaken the Gulf island state, in the early hours of Thursday firing rubber bullets and tear gas and sending hundreds of protesters fleeing.
Up to 95 protesters were wounded in the operation which was launched without warning at around 3.00 am (midnight GMT), opposition members and witnesses said.
"They attacked the square, where hundreds of people were spending the night in tents," said one witness, 37-year-old Fadel Ahmad.
At the city's main Salmaniya hospital, medical staff was overwhelmed as ambulances and private cars were still ferrying in the injured more than three hours after the assault began.
Relatives of the victims gathered outside the hospital, angry and weeping and while in the course of the day hundreds of people joined them, chanting "Death to Al-Khalifa" -- referring to the royal family.Others queued to donate blood.
During the early morning operation, explosions and ambulance sirens could be heard a few hundred metres (yards) from the central square, which had been sealed off. Demonstrators fled pursued by security forces, as a helicopter flew overhead.
Security forces were later in the morning deployed across Manama, with armed police blocking roads leading to the square and setting up checkpoints in other streets, causing heavy traffic congestion.
Witnesses said dozens of armoured military vehicles were parked near Pearl Square as the military warned "strict measures" would be taken 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 spokesman said in a statement.
The ministry also urged people to "refrain from gathering in vital areas," in Bahrain.
Interior ministry spokesman General Tarek al-Hassan said in an earlier statement that police had had no option but to raid the square.
"The security forces evacuated Pearl Square ... after having exhausted all chance of dialogue," Hassan said, as quoteed by the official news agency BNA.
"Some left the place of their own accord, while others refused to submit to the law, which required an intervention to disperse them," he said.
Thousands of demonstrators inspired by uprisings in Tunisia and Egypt, had been occupying the square since Tuesday, after police killed two young Shiite demonstrators during anti-government protests.
The leader of the main Shiite opposition condemned it as a "savage and unjustified attack against a peaceful assembly."
Sheikh Ali Salman, head of the Islamic National Accord Association (INAA), told AFP: "This attack was a mistaken decision which will have catastrophic repercussions on the stability of Bahrain."
MP Ali al-Aswad said that the Al-Wefaq bloc, which occupies 18 of the 40 parliamentary seats in Bahrain, is "heading towards pulling out" from the parliament and that Salman "will announce something in this regard."
The INAA said riot police had opened fire without warning using rubber bullets.
Protesters had renamed Pearl Square as Tahrir (Liberation) Square, after the area in Cairo that became the focal point of an uprising that finally toppled strongman Hosni Mubarak last Friday after 18 days of nationwide protests.
British Foreign Secretary William Hague called on Bahrain Thursday to exercise restraint and urged its rulers to continue with a programme of reforms, while European Union foreign policy chief Catherine Ashton called on the authorities to respect the right of citizens to protest peacefully.
Before the latest clashes, the White House said Wednesday it was watching the developments "very closely" and called on Bahrain's rulers to allow peaceful anti-government protests.