Four people were killed in clashes with authorities during protest

MANAMA, Bahrain - Armed patrols prowled neighborhoods and tanks appeared in the streets for the first time on Thursday after riot police with tear gas and clubs drove protesters from a main square where they had demanded sweeping political change in this tiny kingdom. Medical officials said four people were killed.

Police cars with flashing blue lights encircled Pearl Square, the site of rallies since Monday. Barbed wire was set up on streets leading to the square, where police cleaned up flattened tents and trampled banners. The Interior Ministry declared the protest camp "illegal" and warned Bahrainis to stay off the streets.

The island nation was effectively shut down since workers in the capital could not pass checkpoints or were too scared to venture out. Banks and other key institutions did not open.

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 Shiites who claim they face systematic discrimination and are effectively blocked from key roles in public service and the military.

Tiny Bahrain also is a pillar of Washington's military framework in the region. It hosts the US Navy's 5th Fleet, which is a critical counterbalance to Iran's efforts to expand its clout in the region.

Any prolonged crisis opens the door for a potential flashpoint between Iran and its Arab rivals in the Gulf. Bahrain's ruling Sunni dynasty is closely allied to Saudi Arabia and the other Arab regimes in the Gulf. But Shiite hard-liners in Iran have often expressed kinship and support for Bahrain's Shiite majority, which accounts for 70 percent of the island's 500,000 citizens.

Sporadic clashes between police and protesters continued in the morning, with demonstrators hurling rocks, then retreating. A group of young men broke up the pavement for more stones to throw.

A body covered in a white sheet lay in a pool of blood on the side of a road. Police cleared away the wrecked tents, and the street was littered with broken glass, tear gas canisters and other debris.

Demonstrators began camping out on Tuesday on the square beneath the 90-meter monument featuring a giant pearl, making it the nerve center of the first anti-government protests to reach the Gulf since the uprising in Egypt.

The police assault came early on Thursday with little warning. Mahmoud Mansouri, a protester, said police surrounded the camp and then quickly moved in.

Protest takes a toll

North Sea Brent crude oil extended gains toward $104 a barrel on Thursday, near a two-and-a-half-year high as unrest in the Middle East stoked fears of a disruption of oil flows.

The dollar hit a one-week low against a basket of currencies on worries over rising Middle East tension.

"All in all, the pace of change sweeping the region is truly mind-boggling, and we find it unlikely oil prices will settle any time soon as long as this kind of upheaval continues to spread," said Edward Meir, senior commodity analyst at brokers MF Global.

Brent crude for April delivery rose 10 cents to $103.88, after settling $2.14 higher at $103.78, its highest close since September 2008, and off an earlier intraday high of $104.52.

AP-Reuters