BALI, Indonesia (AP) -- A car bomb ripped through a nightclub packed with foreign tourists on the island of Bali, sparking a blaze that killed at least 187 people and injured 300 others. It was the worst terrorist act in Indonesia's history.

There was no claim of responsibility, but speculation focused on Osama bin Laden's al-Qaida network, which U.S. officials have said operates in Indonesia, the world's most populous Muslim nation.

``We are very much considering this a despicable act of terrorism,'' U.S. Ambassador to Indonesia Ralph Boyce said. The bombing Saturday was on the second anniversary of the al-Qaida linked attack against USS Cole off Yemen that left 17 sailors dead.

After the car bombing, bloodied survivors fled the Sari Club at the Kuta Beach resort, some with limbs blown off. Cars and motorbikes on the road in front of the club were alight, forming a wall of flames blocking people's escape.

``Some poor (man) was laying right on the corner and one of his legs was gone,'' said Bruce Baker, a tourist from Australia's Gold Coast. ``He was quite coherent, he was just saying, 'What's going to happen to me?' I said to him, `You'll be right, mate, someone will come.'''

Seconds before the main blast, what police said was likely a homemade bomb exploded outside another club about 30 yards away. A third bomb exploded near the island's U.S. consular office, but there were no casualties.

Officials said Australians, Canadians, Britons and Swedes were killed along with Indonesians. U.S. officials said they didn't know if there were any Americans among the casualties. Bali is a popular tourist destination with Australians.

President Bush condemned the attack and offered the nation's sympathy to Indonesia and help to find the perpetrators.

Bush also singled out Australia -- where many of the victims came from -- noting that the United States' ``prayers are also with our friends and allies, the people of Australia, who are suffering a grevious personal and national loss.''

The blasts came three days after the U.S. State Department issued a worldwide alert for terror attacks and highlighted fears by the United States and others that Indonesia is becoming a haven for terrorists.

Speaking to CNN, Boyce said that details of al-Qaida activity in Indonesia uncovered in recent weeks ``would indicate that their presence here, as we've always suspected, is in fact one that we can now more or less confirm.''

Asked about Indonesian efforts to crack down on terrorism, Boyce said: ``I think the efforts are going to have to be redoubled, if not more so, in response to this terrible act, and I think I see every evidence that they are intent on doing so.''

In a notice on its Web site, the U.S. Embassy said it ``is still trying to assess the number of American victims,'' while the attack ``highlights the mounting threat to Americans wherever they are in Indonesia.''

The notice said the embassy is ``re-evaluating the extent of its presence in Indonesia'' and warned Americans to be vigilant.

The Indonesian government's crisis center in Bali said 187 people had died and that 309 were hurt, about 90 of them critically.

``This is the worst act of terror in Indonesia's history,'' Gen. Da'i Bachtiar, the national police chief, told reporters at the site of the blast. ``We have to be more alert for other acts of terror.''

President Megawati Sukarnoputri, whose government has been accused by the United States and its neighbors of being slow to respond to the terror threat, flew to Bali and promised to cooperate with the international community in fighting terrorism.

``The bombings, once again, should be a warning for all of us that terrorism constitutes a real danger and potential threat to the national security,'' Megawati said. She later visited the site, tears in her eyes, with security ministers and top generals.

Asked about the suspected origins of the bombers or a possible link to al-Qaida, she said: ``That will be continuously investigated so that this can be uncovered as soon as possible.''

The explosion went off about 11 p.m. in a Jeep-like vehicle and left a huge crater at the entrance to the nightclub, which was located in the center of Kuta. It is Bali's biggest tourist area and a maze of clubs, restaurants, shops, hotels and beach bungalows. It caters to a younger crowd of tourists and surfers.

The blast ignited a huge blaze -- apparently caused by exploding gas cylinders -- which collapsed the flimsy roof structure, trapping hundreds of revelers inside. Footage from Associated Press Television News showed several bodies strewn among the rubble.

``The place was packed, and it went up within a millisecond,'' Simon Quayle, the coach of an Australian rules football team, told Australian Broadcasting Corp. radio.

Quayle, whose team was visiting Bali, said he made it safely out of the building but eight of his 19 players were missing.

The blaze then engulfed a nearby nightclub before racing through about 20 other buildings on the block, heavily damaging many of them.

The second explosive detonated a few minutes after the first in the nearby city of Denpasar, Bali's capital, about 300 feet from a U.S. consular office, Suyatno said.

A bomb squad was investigating both blasts but Indonesian officials declined to provide a motive or blame any group.

Australia's Foreign Minister Alexander Downer blamed the bombings on terrorism.

``We don't know yet who is responsible for this. But the organization we've been very concerned about in Indonesia ... is called Jemaah Islamiyah, and it has certainly been responsible for terrorist attacks over the years,'' Downer said on Sunday.

The group, linked to al-Qaida, allegedly plotted last winter a series of bomb attacks against the U.S., British and Australian embassies and other Western targets in Singapore.

Singapore has been pressing Indonesia to arrest Jemaah Islamiyah's alleged leader, Abu Bakar Bashir, who lives in Indonesia. But Indonesian officials say they have no evidence against him.

Downer said he believed the Sari nightclub was targeted because it was popular with Australians and other foreigners. Australia has also been one of the United States' staunchest allies in its war on terror and has 150 elite troops serving in Afghanistan.

Later Sunday, Australian Prime Minister John Howard said he will launch an urgent review of national security in the wake of the attack. He said the attack demonstrated Australia was not immune from terror.

French President Jacques Chirac said Sunday his country was ready to help Indonesia in every possible way to capture the perpetrators of the ``vile'' bomb attack on the island of Bali.

Wayan Putra, a driver at the nearby Poppies hotel, said that after the blast, hundreds of townspeople rushed toward the nightclub but could not get near it because of the intense flames.

Indonesian officials have denied the claims that terrorists are using Indonesia as a base. But the U.S. Embassy in the national capital of Jakarta closed Sept. 10 and remained shut for six days due to what U.S. officials said were threats possibly linked to al-Qaida.

Days later, a hand grenade exploded in a car near a house belonging to the U.S. Embassy in Jakarta, killing one man. There was conflicting information as to whether the device was meant to harm Americans.