A joint U.S.-Saudi investigation into a series of terrorist bombings that heavily damaged several residential compounds for foreigners in the Saudi capital, Riyadh, has begun. At least 29 people, including seven Americans, are dead in what appears to be closely coordinated suicide attacks Monday night targeting westerners. Although no one has claimed responsibility, Secretary of State Colin Powell suspects the bombings may be the work of al-Qaida.

The Saudi government is calling Monday night's suicide car bombings the work of "criminals" who have no regard for human life. But after touring a damaged apartment building which had its entire front side blown off, Secretary of State Colin Powell went further, telling reporters traveling with him on what had been a previously scheduled visit to the country, the attacks looked to be the work of al-Qaida.

"This was a well-planned terrorist attack, obviously. The facility had been cased as had the others, very well executed, and it shows the nature of the enemy we're working against," he said.

Saudi Crown Prince Abdullah, the kingdom's defacto ruler, read a statement on state television Tuesday night but stopped short of saying who authorities believe was responsible. It appeared to be an attempt to reassure foreign residents that the Saudi capital, Riyadh, remains safe.

He spoke through a translator. "If they were thinking that they would just shake the security in our country, they are just dreaming," he said.

Still, governments including the United States and Britain are urging their citizens to avoid travel to Saudi Arabia or consider leaving. Earlier this month, the State Department issued an unusually explicit warning that terrorists in the Saudi kingdom may be in the final phases of planning attacks. And just days later, in an unusually candid admission, Saudi officials announced the discovery of a large weapons cache and what they described as an alleged plot by followers of Osama bin-Laden to carry out a terrorist attack.

U.S. officials are not saying whether they believe Monday night's attack was part of that plan. But the FBI is on its way to Saudi Arabia to take part in a joint investigation into one of the deadliest attacks against Americans since September 11, 2001.

President Bush, speaking to supporters in the state of Indiana, vowed those responsible for the Saudi blasts will be caught.

"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," he said.

But no one has yet been brought to justice in the United States for the deaths in Saudi Arabia seven years ago of 19 American servicemen, killed in a truck bomb near Dhahran. Thirteen Saudi suspects were indicted on charges of murder in connection with that attack.