KHOBAR, Saudi Arabia - Saudi forces combed the kingdom on Monday for suspected al Qaeda militants who killed 22 civilians and took dozens of foreigners hostage in a daring attack on its globally vital oil industry.
Security forces set up nationwide checkpoints after three gunmen, using hostages as human shields, escaped Saudi commandos who stormed a residential compound in the eastern oil city of Khobar on Sunday to end a 25-hour siege.
All the hostages who had not been killed were freed.
The kingdom is the world's largest crude oil exporter and state-owned giant Saudi Aramco vowed to keep supplies flowing smoothly in a bid to avert a hike in already-high world oil prices. Most energy markets will not reopen until Tuesday.
The Interior Ministry said a total of 41 people had been held hostage and 201 trapped inside the compound. A Saudi diplomat said nine hostages were killed during the stand-off.
Rescued hostages said none of the civilians had been killed by security forces and one of the staff at the complex said Saudi forces let the gunmen out after they threatened to blow up themselves and their captives.
An internet statement purporting to come from al Qaeda said Osama bin Laden's network had carried out the assault and the unprecedented hostage-taking, which raised the stakes in the battle Saudi Arabia has waged with the group for a year.
The bloodbath began on Saturday when gunmen in military garb opened fire on the Al-Khobar Petroleum Centre building, housing offices of major Western oil firms, before storming into compounds containing oil services offices and employees' homes.
"There were pools of blood, blood is everywhere," said a member of the staff at the upmarket Oasis compound, adding that freed hostages told him there had been more than four attackers.
The hotel where the foreign hostages were held was still sealed off after the siege and security forces were searching for explosives the militants might have left behind.
Bullet-holes, blood stains, shattered glass, empty cartridges and grenades were evidence of the havoc, he said.
A hostage heard the gunmen shouting that they would release their captives if the security forces let them go, the compound employee said.
"The security forces refused at the beginning but then apparently relented," he said. "There was a kind of a deal reached to let the hostages go free, though some hostages had already been killed."
The Interior Ministry said in a statement three gunmen escaped but that Saudi forces wounded and captured their leader.
The Khobar assault was the second in less than a month on the Saudi oil industry, a lifeline of the world economy. The attacks appear aimed at overthrowing the Saudi monarchy.
Arab residents had said the gunmen asked them if they were Muslim or Christian before targeting the Christians.
"It happened very quickly. It's difficult to recall it all. I locked the front door and I heard some shots," said Diane Reed, an American shot in the legs when the militants first stormed the complex on Saturday. She was at al-Saad hospital where she underwent two surgeries.
The ministry listed the total death toll in the attack as an American, a Briton, an Italian, a South African, a Swede, eight Indians, two Sri Lankans, three Filipinos, an Egyptian boy and three Saudis. It said 25 people were injured.
Saudi Arabia's highest religious authority said the attackers were puppets manipulated by the kingdom's foes.
"Enemies exploited them and made them puppets to do their bidding. The killers are controlled by people who are targeting our faith and our security," Sheikh Abdulaziz bin Abdullah Al-Sheikh was quoted as saying in Saudi-owned daily al-Hayat.
The statement purported to be from al Qaeda said the attack was the result of "detailed observation" and included live recordings of the gunmen as they stormed the Oasis compound.
"Open the door, open the door! Come on, quickly," a voice was heard shouting over sounds of gunshots and bangs.
Top al Qaeda leader in Saudi Arabia, Abdulaziz al-Muqrin, vowed that 2004 would be "bloody and miserable" for the kingdom. Last week he issued plans for urban guerrilla warfare.
Al Qaeda wants to destabilise the country, whose leaders it considers subservient to the West. In 1996, the then little known group chose Khobar to mount one of its first major attacks, blowing up a compound and killing 19 US soldiers.
A Briton's body was dragged through the streets behind a car on Saturday, witnesses said. An American suffered the same fate during an attack on a petrochemical site in the Red Sea town of Yanbu earlier this month.