Gemayel, a 34-year-old Christian Maronite politician, was critically wounded in the attack and died soon afterwards in a nearby hospital, the source said.

The state news agency said Gemayel was killed "by gunshots on his convoy near the Mar Antonios church in the region of Jdaideh," north of Beirut.

Witnesses said Gemayel was apparently driving the car when it was attacked by gunmen, who shot him in the head.

The window on the driver's side was riddled with bullet holes.

Dozens of family members and friends rushed to the hospital, many of them shouting in anger and others wailing. One woman was evacuated after fainting in the emergency ward.

Lebanese television channels interrupted their normal broadcasts to air classical music after the death was confirmed.

The head of the anti-Syrian majority in parliament, Saad Hariri, interrupted a press conference to accuse the Syrian regime of "trying to kill every free person" in Lebanon.

"The cycle (of killings) has resumed," he said.

He was referring to a spate of assassinations and attempts in the past two years. These included the murder of his own father, five-time premier Rafiq Hariri, in a massive bomb blast on the Beirut seafront in February last year.

Hariri later told CNN he believed the killing was linked to a looming UN Security Council decision on endorsing an international tribunal to try suspects in the murder of his slain father.

"We believe that the hands of Syria are all over the place," he said.

"This is not a time to give up. Blood has been shed to free our country from the hands of the regime, from the regime that was involved in killing Rafiq Hariri, in killing a lot of people," he said.

A UN probe has implicated senior Syrian officials and their Lebanese allies in Hariri's murder, which sparked protests that forced Damascus to end nearly three decades of military domination in Lebanon.

The Syrian regime has denied links with the attacks.

Gemayel was the son of former president Amin Gemayel, a leading figure of the anti-Syrian camp. He was also the nephew of president-elect Bashir Gemayel, who was murdered in 1982 at the height of Lebanon's 15-year civil war.

He is also the grandson of Pierre Gemayel, the founder of the Christian Kataeb (Phalangist) party.