The US-led attack on Iraq has sparked angry protests across the Arabian peninsula with the most violent in Yemen, where authorities seem at a loss as to how to control almost universal anti-war sentiment.

Hundreds of thousands of Yemenis took to the streets against the war even before it began. A day after the initial US-British strike on Thursday, protesters clashed violently with police who blocked them from marching on the US embassy in Sanaa.

Authorities said two people were killed, although a police officer had earlier said four were dead. No Yemeni in a position of authority defends the US position, with daily denunciations by the government, religious leaders and unions of the "aggression" against the fellow Arab state.

The government has mostly followed the lead of the 18 million people in Yemen, which is largely tribal in tradition and where weapons are in wide circulation.

President Ali Abdullah Saleh, who allied himself with the United States in the post-September 11 "war on terrorism", despite Yemen's reputation as an al-Qaeda hotbed, has recognized that public opinion here "is opposed to the war against Iraq." But he has called on Yemenis to "demonstrate peacefully" within the bounds of the law, and around 10 opposition leaders face charges in connection with the turbulent anti-war protests.

On Monday, Yemen's parliament denounced the war on Iraq as aggression that targets "the entire Arab and Islamic nation" and urged Arab rulers "to shoulder their responsibilities towards the Iraqi and Palestinian peoples."

The influential association of ulemas, or religious scholars, went so far as to call the war on Iraq "a violation of divine laws and international conventions."

The clerics ruled that "any form of moral or material assistance to the aggressors and invaders is forbidden." A group of opposition figures separately called on Arab countries to expel US ambassadors.

Angry anti-US protests have also been seen in Gulf Arab states, some of which have hosted US and British military forces.

In Bahrain, young protesters have tried several times to attack US installations. On Monday, a gas bottle was blown up near the headquarters of the US Navy's Fifth Fleet, although there were no injuries or damage.

When the war began Thursday, Bahrain's Emir Sheikh Hamad bin Issa al-Khalifa, who has been trying to encourage more political openness, urged people to remain calm and voiced hope that a solution to the Israeli-Palestinian conflict, a major issue for many demonstrators, would be found once the Iraq war finished.

In Oman, which rarely sees the same commotion as other states on the peninsula, there have been two anti-war demonstrations attended by hundreds of people, including Arab expatriates.

The streets of Saudi Arabia and the United Arab Emirates, which bar public demonstrations, have been silent, as they have in Qatar, which is hosting the US military command.

There has also been little anti-war protest in Kuwait, whose 1990-91 occupation by Iraq was ended by a US-led coalition. In recent months, however, two people have been killed in anti-US attacks in the emirate - Sapa-AFP