[WARNING: This video contains images that some viewers may find disturbing]
Troops and tanks have locked down the Bahraini capital of Manama on Thursday after riot police swinging clubs and firing tear gas smashed into demonstrators in a pre-dawn assault, killing at least four people.
Hours after the attack on Manama's main Pearl Roundabout, the military announced a ban on gatherings, saying on state TV that it had "key parts" of the capital under its control.
Khalid Al Khalifa, Bahrain's foreign minister, justified the crackdown as necessary because the demonstrators were "polarising the country" and pushing it to the "brink of the sectarian abyss".
Speaking to reporters after meeting with his Gulf counterparts, he also said the violence was “regrettable”. Two people had died in police firing on the protesters prior to Thursday's deadly police raid.
An Al Jazeera correspondent, who cannot be named for security reasons, said that hospitals are full of injured people after Wednesday night's police raid on the pro-reform demonstrators.
"Some of them are severely injured with gunshots. Patients include doctors and emergency personnel who were overrun by the police while trying to attend to the wounded."
Another Al Jazeera online producer said that booms could be heard from different parts of the city, suggesting that "tear-gas is being used to disperse the protesters in several neighbourhoods".
After several days of holding back, the island nation's Sunni rulers unleashed a heavy crackdown, trying to stamp out the first anti-government upheaval to reach the Arab states of the Gulf since the uprisings in Tunisia and Egypt.
In the surprise assault, police tore down protesters' tents, beating men and women inside and blasting some with shotgun sprays of bird-shot.
'They made us angrier'
The pre-dawn raid was a sign of how deeply the Sunni monarchy fears the repercussions of a prolonged wave of protests, led by members of the country's Shia majority but also joined by growing numbers of discontented Sunnis.
Tiny Bahrain is a pillar of US's military framework in the region. It hosts the US Navy's 5th Fleet, which Washington sees as a critical counterbalance to Iran.
Bahrain's rulers and their Arab allies depict any sign of unrest among their Shia populations as a move by neighbouring Shia-majority Iran to expand its clout in the region. The army would take every measure necessary to preserve security, the interior ministry said.
But the assault may only further enrage protesters, who before the attack had called for large rallies on Friday.
|Tents at the Pearl Roundabout in Manama were cleared of protesters by riot police [Reuters]
In the wake of the bloodshed, angry demonstrators chanted "the regime must go," and burned pictures of King Hamad bin Isa Al Khalifa outside the emergency ward at Salmaniya Medical Complex, the main hospital in Manama.
"We are even angrier now. They think they can clamp down on us, but they have made us angrier," Makki Abu Taki, whose son was killed in the assault, shouted in the hospital morgue.
"We will take to the streets in larger numbers and honour our martyrs. The time for Al Khalifa has ended."
UK reviews arms sales
Meanwhile, Britain said Thursday it was reviewing decisions to export arms to Bahrain after anti-government demonstrators were killed in clashes with security forces.
"In light of events we are today formally reviewing recent licencing decisions for exports to Bahrain," said Alistair Burt, a junior foreign minister with responsibility for the Middle East.
He warned that Britain would "urgently revoke licences if we judge that they are no longer in line with the criteria" used for the export of weapons.
In a statement, the minister said a range of licences had been approved for Bahrain in the last nine months.
"These include two single export licences for 250 tear gas cartridges to the Bahrain Defence Force and National Security Agency that were for trial/evaluation purposes."
Hillary Clinton, the US Secretary of State, called Bahrain's foreign minister to register Washington's "deep concern" and urge restraint.
Similarly, Human Rights Watch called on Bahraini authorities to order security forces to stop attacks on peaceful protesters and investigate the deaths.
Salmaniya hospital was thrown into chaos by a stream of dozens of wounded from Pearl Roundabout, brought in by ambulances and private cars.
At least one of the bodies of the victims had signs of bloody holes from pellets fired from police shotguns.
Nurses rushed in men and women on stretchers, their heads bleeding, arms in casts, faces bruised. At the entrance, women wrapped in black robes embraced each other and wept.
Siege in the capital
The capital Manama was effectively shut down on Thursday. For the first time in the crisis, tanks rolled into the streets and military checkpoints were set up as army patrols circulated.
The Interior Ministry warned Bahrainis to stay off the streets. Banks and other key institutions did not open, and workers stayed home, unable or too afraid to pass through checkpoints to get to their jobs.
Barbed wire and police cars with flashing blue lights encircled Pearl Roundabout, the site of pro-reform rallies since Monday.
The area was turned into a field of flattened tents, and the strewn belongings of the protesters, who had camped there litter the site.
Banners lay trampled on the ground, littered with broken glass, tear gas canisters and debris. A body covered in a white sheet lay in a pool of blood on the side of a road nearby.
Bahrain's state television aired footage from the Bahrain interior ministry showing swords, knives and other bladed instruments, as well as pistols and bullets, which police said were found in tents of the pro-reform demonstrators.
Demonstrators had been camping out for days around the landmark roundabout's 90-metre monument featuring a giant pearl, a testament to the island's pearl-diving past.
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 deep grievances held by the country's majority Shia who make up 70 per cent of Bahrain's 500,000 citizens but claim they face systematic discrimination and poverty and are effectively blocked from key roles in public service and the military.