RIYADH, Saudi Arabia – The terror attack that killed at least 20 people in Riyadh Monday night "had the earmarks of Al Qaeda," Secretary of State Colin Powell (search) said Tuesday.
President Bush vowed to track down the people who plotted the attack and bring them to justice. And Saudi Crown Prince Abdullah (search) said in a televised news conference that terrorists are "like monsters . . . devoid of all Islamic values."
One hour after saying that 91 people had been killed, a State Department official said the actual figure was much closer to the Saudi estimate of 29, including nine homicide bombers whose charred bodies were found at the scene of the explosions.
At least 40 other Americans reportedly were wounded.
Powell initially said that 10 Americans had been killed, but that number was later lowered to eight.
No group has claimed responsibility for the coordinated attacks on three housing compounds, but Powell said Al Qaeda (search) terrorists were the prime suspects.
"It certainly has all the fingerprints of an Al Qaeda operation," he said.
The bombings, which took place about 11:30 p.m. Monday, constituted one of the deadliest terror attacks on Americans since Sept. 11, 2001.
Terrorists simultaneously shot their way into the compounds, then set off homicide car bombs.
"If they believe that their criminality ... will shake even one hair on the body of our nation and its unity, then they are deceiving themselves," said Abdullah, who essentially runs Saudi Arabia.
"There is no place for terror, but there is a place for decisive deterrence against them."
The bombings wounded 194 people, most of them slightly, a Saudi official said.
"Terrorism strikes everywhere and everyone," Powell said after he arrived in the Saudi capital. "It is a threat to the civilized world." He said there was "a large loss of life of others."
Powell later visited the sites and called the bombings "well planned terrorist attacks."
"It shows the nature of the enemy we're working against," he said. "These are people who are determined to try to penetrate facilities like this for the purpose of killing people in their sleep, killing innocent people, killing people who would try to help others.
President Bush, in a speech at the Indiana State Fairgrounds, denounced the bombings as the work of "killers whose only faith is hate." He vowed to "find the killers and they will learn the meaning of American justice."
"Anytime anybody attacks our homeland, or our fellow citizens, we will be on the hunt," Bush said. "We will bring them to justice. Just ask the Taliban."
U.S. Embassy spokesman John Burgess told Fox News that the embassy sent out a "warden" message advising all Americans in Saudi Arabia to remain at home.
Several members of the Saudi National Guard were reportedly killed.
A smaller bombing Tuesday near the headquarters of a Saudi-U.S. company didn't cause any casualties.
At the housing complexes Tuesday, five floors of buildings were blown out and building facades were sheared off. Heaps of rubble and blocks of upended concrete surrounded twisted steel bars and downed palm trees. Burned-out hulks of cars were still in their parking spots; upended furniture and debris littered a pool deck.
Compound residents tend to be professionals in the oil industry, the financial sector or schools. The compounds housed families of Boeing Co., and the Virginia-based Vinnell Corp., which has a contract to train Saudi military and civilian officials.
Saudi Arabia has a large population of expatriate workers, including about 35,000 Americans.
One survivor, John Gardiner from Kinghorn, Scotland, told the BBC that the blasts were "absolutely terrifying."
A compound guard told the Saudi paper al-Watan that seven cars carrying homicide bombers exploded near the northeastern corner of the city. At least three bodies could be seen lying on the ground there Tuesday morning.
"It is no consolation, but these things happen everywhere," said Saudi Foreign Minister Prince Saud. "It should increase our efforts and should make us not hesitate to take whatever measures that are needed to oppose these people, who know only hate, only killing."
Al Qaeda is known for homicide bombings and the Sept. 11 attacks and the 1998 car bombings outside American embassies in Kenya and Tanzania that killed some 230 people.
"It smells like Al Qaeda," terrorism expert Harvey Kushner told Fox News. "This is a clear signal to me that the United States still needs to be on alert not only inside the United States but outside."
The Bush administration has said about 60 countries have been infiltrated by Al Qaeda.
Former CIA intelligence officer Peter Brookes said the scale, sophistication and calculation of Monday's attack "smacks of Al Qaeda."
Brookes called the bombing a "real wake up call" for Saudi Arabia and said the United States and Saudi Arabia need to work more closely to crack down on terrorism.
"Al Qaeda's structures have been weakened, but we must assume that they are still able to carry out operations," said German Interior Minister Otto Schily. "If it turns out that the Riyadh attacks can be attributed to Al Qaeda … this would bolster our assessment."
Added Jordanian Foreign Minister Marwan Muasher: "This will only strengthen our resolve to find a solution to all the problems of the region."
Recent U.S. intelligence information indicated that Al Qaeda was planning a strike in Saudi Arabia, birthplace of Usama bin Laden and home to Islam's holiest sites.
"There was plenty of chatter beforehand saying they were going to do something like this," one senior administration official told Fox News. "There are people claiming to be Al Qaeda saying they were responsible."
The United States is pulling out most of the 5,000 troops it had based in Saudi Arabia, whose presence fueled anti-American sentiment
Bin Laden has repeatedly railed against the presence of what he calls "infidel" troops on Muslim holy land.
"We will track them down," one Saudi official told Fox News. "It is very sophisticated explosives, not stuff you could make in a basement. This was a synchronized, planned attack."
The Saudi Interior Minister, Prince Nayef, said the assailants likely were linked to the discovery of a large weapons cache on May 6.
The Saudi government is hunting 19 suspects in that case — including 17 Saudis, a Yemeni, and an Iraqi with Kuwaiti and Canadian citizenship — who it believed were Al Qaeda sympathizers receiving orders from bin Laden.
The group may have been planning an attack on the Saudi royal family and American and British interests.
Nayef told the al-Watan newspaper that one suspect was being interrogated about Monday's explosions. So far he had offered "limited information," Nayef said. The communities attacked Monday were in the same part of the city where the weapons seizure was made.
The Mujahedeen in the Arabian Peninsula had linked itself to the cache and over the weekend vowed on an Internet site to strike American targets worldwide.
In response to the months of criticisms and allegations that Saudi Arabia funded terrorist and Al Qaeda groups, one Saudi official told Fox News: "Why would our government fund an organization that wants to target Saudi Arabia?"
State Department officials advised Americans to remain at home.
Earlier this month, it advised Americans against traveling to Saudi Arabia because of terrorism concerns. Americans have historically been targeted in terror attacks in that region.
"The fact that they have attacked three compounds in a coordinated way sends a message to the Western community that we are not safe here. It's like they're saying, 'We can get you any time, anywhere,'" British telecommunications executive John Crossley told the Los Angeles Times.
Fox News' Jim Angle, Bret Baier, Wendell Goler and Liza Porteus and The Associated Press contributed to this report.
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