BEIRUT, Lebanon -- Pierre Gemayel was leaving church when he fell victim to a well-coordinated hit: One vehicle cut off his car from the front, another rammed him from behind, then gunmen burst out and sprayed bullets into his passenger-side window.

When the scion of Lebanon's most prominent Christian political family was pronounced dead at a nearby hospital, riddled with eight shots, supporters vowed vengeance against Syria and its Lebanese supporters. Bands of young Christians broke car windows and burned tires and garbage cans in parts of Beirut and in the Gemayel family's mountain stronghold nearby.

The assassination Tuesday pushed Lebanon's already dangerous political crisis between the U.S.-backed government and the Syrian-backed Hezbollah one step closer to an explosion.

President Bush condemned the killing and accused Syria and Iran of seeking to undermine Prime Minister Fuad Saniora's government. Bush stopped short of specifically blaming them for Gemayel's death, though the U.S. ambassador to the United Nations, John R. Bolton, raised the possibility.

Anti-Syrian politicians in Lebanon, however, directly pointed the finger at Damascus. A funeral was set for Thursday in downtown Beirut, with the anti-Syrian factions calling for mass participation, raising worries over street violence.

Politicians from all sides scrambled to contain the fallout of the assassination, urging calm amid fears of an outbreak of the brutal violence between Lebanon's sharply divided communities that marked the 1975-1990 civil war.

Former president Amin Gemayel -- Pierre's father and leader of the Phalange Party -- urged his supporters to observe a night of "prayer and reflection."

"We don't want an outburst of emotions and revenge," he said outside the hospital where his son died. "He was martyred for the cause of Lebanon, and we want this cause to triumph."

The killing sent tensions spiraling at a time when Lebanon was already facing a worsening political crisis. The Shiite Muslim guerrilla group Hezbollah and its pro-Syrian allies have threatened massive protests -- as early as Thursday -- aimed at bringing down Saniora's government unless it gives them greater power.

Saniora's government is dominated by opponents of Syria. Many see the demands as a bid by Damascus to restore its influence in its smaller neighbor -- and by Hezbollah to boost its power, riding on increased popularity among Lebanon's Shiite Muslim population following this summer's war with Israel.

The 34-year-old Pierre Gemayel, an outspoken opponent of Hezbollah, was the fifth anti-Syrian figure killed in the past two years and the first member of the Saniora government to be slain. Many in Lebanon have accused Damascus in the previous assassinations, including the 2005 bomb blast that killed former prime minister Rafik Hariri, a claim Syria has denied.

Syria and Iran both condemned Gemayel's slaying, and Syrian Information Minister Mohsen Bilal denied Syria had any role. "Those who are accusing Syria in this sick way ... do not have an iota of truth or credibility," he said on Al-Jazeera.

Tuesday's hit came hours before the U.N. Security Council endorsed a draft document creating the international court to try suspects in the Hariri murder, in which an U.N. investigation has implicated several Syrian officials. The document then goes to the Lebanese government for final approval.

With the possibly explosive atmosphere following Tuesday's assassination, it was not clear whether Hezbollah would go ahead with its threat to hold massive anti-government demonstrations. If it does, it would throw Lebanon deeper into turmoil, putting it into confrontation with many Gemayel supporters now itching for a fight.

Gemayel, the industry minister, was the rising star of his Maronite Christian political family, which has seen four other members killed in the past three decades of Lebanon's violence.

Past attacks on Gemayel's family have sparked brutal reprisals. A 1975 assassination attempt against his grandfather, also named Pierre, prompted Phalangists to attack a busload of Palestinian refugees in what became the spark of a 15-year sectarian civil war. After the killing of Amin Gemayel's brother, Bashir, in a 1982 explosion, his militia supporters stormed Palestinian refugee camps in Beirut, killing hundreds of unarmed civilians in one of the worst atrocities of the Lebanon conflict.

On Tuesday, Gemayel was traveling through his mainly Christian constituency of Jdeideh when a vehicle in front of his slammed to a stop, causing his car to ram into it, security officials said. Witnesses said Gemayel's car was also rammed from behind.

Three gunmen stepped out of the other vehicles and shot Gemayel at point-blank range with automatic weapons fitted with silencers, security officials said.

Video showed Gemayel's car, which apparently had been shot at from both sides: The passenger-side window was shattered and the driver's-side window was dotted with about a dozen bullet holes, and the front hood was crumpled.

Gemayel's driver and another person in the car were wounded. They were rushed to a hospital where Gemayel was pronounced dead. The driver died later Tuesday. The attackers fled.

At the hospital, some 300 supporters called for vengeance, many of them chanting slogans against Hezbollah leader Hassan Nasrallah, pro-Syrian President Emile Lahoud and Hezbollah's Christian ally, Michel Aoun.

"We want revenge from Hezbollah and the General (Aoun)!" young men shouted, shaking their fists in the air.

Other Phalange supporters, including women, screamed and wept. They called on supporters to march to a nearby Shiite neighborhood and Aoun's residence in a Christian suburb east of Beirut.

"Nasrallah, Aoun and Lahoud, they killed him," shouted Antoine Shaaya, a man in his late 20s who wore a large cross around his neck. "And we won't be silent after today."