President Bush has vowed that America will find the attackers responsible for the bombings which are believed to have killed 91 people in Saudi Arabia. Ten of the dead are Americans and at least five Britons have been injured in the three synchronised attacks which targeted Westerners living in the Saudi capital, Riyadh. Bush said: "These despicable acts were committed by killers whose only faith is hate and the United States will find the killers and they will learn the meaning of American justice." The Foreign Office has warned against travelling to Saudi Arabia following the attacks and said there remained a "high threat" of further attacks, possibly using "chemical or biological materials". **Fireballs*** The US is set to order all non-essential diplomats and the families of embassy and consular staff out of Saudi Arabia in the wake of the attacks. In each of Monday night's blasts, gunmen driving vans packed with explosives shot their way into residential complexes where large numbers of western and other foreign nationals lived before detonating their bombs. They exploded with such force that fireballs could be seen in the night sky and entire walls of apartment blocks collapsed. Unconfirmed reports said the son of Riyadh's deputy governor, Abdullah al-Blaihed, an Australian, a Lebanese man and two children are among the dead. The London-based Arabic magazine Al-Majallah said al Qaeda had implied it was behind the attack and, earlier, US Secretary of State Colin Powell said he believed the attacks bore all the hallmarks of the terror group. Bush said he would not be surprised if investigations showed al Qaeda was responsible. "I can't say for certain it was al Qaeda yet but I wouldn't be surprised if it was," he said. A fourth explosion targeted the headquarters of Siyanco - a joint US-Saudi-owned company. **PHOTO CAPTION*** A Saudi police officer looks on, as civil defense personnel search for bodies in the debris of the Al-Hamra housing compound, in Riyadh, Saudi Arabia, Tuesday May 13, 2002. (AP Photo/Ali Fraidoon)