BEIRUT, Lebanon (AP) – A massive bomb, a huge crater. Cars ablaze. And an assassinated leader. Bloody images from the past played out once again in the streets of Beirut.

The killing of former Prime Minister Rafik Hariri revived fears that this country – flourishing after 15 years of civil war – might plunge anew into a period of political violence.

The blast that killed Hariri and nine others came, ironically, in the very downtown district he helped to rebuild. Just blocks from the blast site and its deep crater, tourists have returned in recent years to gather at sidewalk cafes under buildings rebuilt in warm yellow stone.

Whether Beirut can resume its old aura as the Paris of the Middle East, however, now seems more uncertain.

Yet the blast Monday and the setback it represents do not mean civil war, not as it was between 1975 and 1990, when religious and sectarian groups fought bitterly.

Instead, the political debate over Syria’s influence that turned ugly on Monday cuts across religious lines. And Hariri, a Sunni Muslim, had many allies in the Christian camp.

Still, the smoldering wreckage and 30-foot crater on a boulevard near the Mediterranean Sea were scenes the Lebanese hoped they would never see again.

The United States called the attack “a terrible reminder” that Lebanon still must shake free of occupation by Syria – the neighbor that keeps 15,000 troops here and influences virtually all key political decisions.

Syria denied any role and condemned the assassination. But opposition leaders in Lebanon said they held both the Lebanese and Syrian governments responsible and demanded that Syrian troops withdraw.

A U.S. official, speaking on condition of anonymity, said it was too early to know who was responsible, but said any list of suspects “would have to include the Syrians and their surrogates in Lebanon.”

Hariri, 60, left office in October but had the wealth and the prominence to maintain some degree of independence from Syria, while never moving toward total defiance.

His shift toward the opposition in recent months had given a boost to calls for Syrian withdrawal – and his death silenced an influential and moderate voice that could prove hard to replace.

It was unclear if his killing would delay parliamentary elections that had been expected in April and May.

Top government officials met in emergency session, then instructed the army and internal security forces “to take all necessary measures to control the security situation.”

The Supreme Council for Defense, which groups the president, Cabinet ministers and military officials, also declared three days of national mourning.

Later in the day, the army command announced forces were on maximum alert and that soldiers and officers were being recalled from vacation or leave. It also said troops were setting up checkpoints and patrolling the streets.

The official National News Agency said Hariri’s funeral would be Wednesday in a Beirut mosque.

President Emile Lahoud, a longtime rival of Hariri, called his killing “a dark point in our national history.” He promised the assassins would be brought to justice.

There were no credible claims of responsibility. A previously unknown group, Support and Jihad in Syria and Lebanon, said in a video broadcast on Al-Jazeera television that it carried out the bombing, which it termed a suicide operation.

Security authorities raided the west Beirut home of Ahmed Abu Adas, a Palestinian they said appeared in the video who fled during the day. They confiscated computers, tapes and documents, the Interior Ministry said.

The midday blast tore through Hariri’s motorcade a block from the famed Mediterranean-side corniche and was so powerful it left the bulletproof vehicles a burning, smoldering wreck. The explosion gouged a crater in the street 30 feet wide and 9 feet deep and shattered windows and twisted metal window frames at a nearby British bank and the landmark Phoenicia Hotel.

Twenty cars were set ablaze. Former Economy Minister Bassel Fleihan, a member of parliament in Hariri’s bloc, was among those severely wounded.

More than 650 pounds of TNT explosives were used in the bombing, security officials said. They did not say whether the explosives were placed in a vehicle or on the street.

Hariri’s supporters quickly took to the streets, many weeping. In his hometown of Sidon, shops were shuttered as hundreds of people poured outside, some of them shouting anti-Syrian slogans. One group of people attacked a van carrying Syrian workers, shattering its windshields.

In Paris, Lebanon’s most prominent exile, former army commander Gen. Michel Aoun, blamed Syria and what he called the “feeble regime imposed by Syria” for the assassination.

But Syrian Information Minister Mahdi Dakhlallah called the killing “a criminial, terrorist action against Lebanon and Syria.”

Asked about Lebanese opposition accusations that Syria had a hand in the attack, Dakhlallah said, “No serious man would address such accusations to Syria. Such talk is nonsense.”

Syrian President Bashar Assad said he “condemned this horrible criminal action,” according to Syria’s official news agency, and urged the Lebanese people to reject those who plant “schism among the people” during this “critical situation.”

In Washington – which has put intense recent pressure on Syria to withdraw its troops – President Bush was “shocked and angered” by the assassination, White House press secretary Scott McClellan said.

“This murder today is a terrible reminder that the Lebanese people must be able to pursue their aspirations and determine their own political future, free from violence, and intimidation and free from Syrian occupation,” McClellan said.

President Jacques Chirac of France, a friend of Hariri, demanded an international investigation, saying Hariri represented “the indefatigable will of independence, freedom and democracy” for Lebanon.

Hariri was an important symbol of Lebanon’s rebirth after its civil war. Under Hariri, European investment in Lebanon rebounded, and tourists, particularly from the Arab world and to a lesser extent Europe, returned to the country.

A self-made construction tycoon who made his fortune in Saudi Arabia, Hariri became prime minister in 1992 under a peace deal that ended the civil war and required the prime minister be a Sunni.

In all, he had served as prime minister for 10 of the 14 years in the postwar period starting in 1992 – winning three separate elections.

Hariri moved toward the opposition camp after leaving office in October – in large part because of a dispute involving Syria. Hariri had rejected a Syrian-backed demand that his rival, Lahoud, remain in office as president for a longer period.

Explosions in Beirut – while common during the 1975-90 civil war – have become rare as the country largely enjoyed a return to peace. In October, however, amid rising tensions between the government and opposition groups, a car bomb seriously wounded an opposition politician and killed his driver in Beirut.

The scene Monday was once again of devastation – reminding many of the civil war.

Bystanders and ambulance workers made crude stretchers for the wounded. Rubble and twisted debris covered a road lined with burning cars, and smoke enveloped the area as firefighters raced to put out the flames.