BEIRUT (AFP) – Lebanon was on high high alert after former minister Rafiq Hariri, architect of the country’s post-war reconstruction, was killed in an attack that has triggered fears of a return to civil chaos.

Several fingers of blame were pointed at the regime in neighbouring Damascus, whose dominant role in Lebanon’s affairs was opposed by Hariri, a billionaire businesssman and five-time prime minister.

Soldiers were patrolling the streets as Lebanon’s army command ordered a mobilisation of all its units to “safeguard stability,” raising its state of alert to the maximum and suspending all leave.

The country also began a three-day mourning period for the 60-year-old Hariri who was killed along with at least nine others when a massive explosion ripped through his motorcade on Monday in an attack condemned across the globe.

Some media reports spoke of as many as 15 dead. About 100 people were also wounded in the blast that left a trail of burnt and bloodied bodies, blazing cars and rubble strewn across a busy seafront area in central Beirut in scenes reminiscent of the 1975-1990 war.

Hariri was “assassinated in a way that brings the ghosts of the not-so distant past howling into present-day reality”, Lebanon’s English-language Daily Star said.

“The pressing concern of the moment is how to prevent Lebanon from tottering over the brink of an abyss.”

A hitherto unknown Islamist group claimed responsibility for what it said was a suicide attack to avenge Hariri’s close ties with the Saudi regime.

Lebanese police raided the home of a Palestinian with the name of a man identified in the group’s video claim but failed to find the suspect.

The dead included six bodyguards of the rags-to riches Sunni Muslim who resigned as prime minister four months ago in a row over Syrian dominance of Lebanon and the continued presence of about 14,000 troops on its soil.

Relatives of Hariri said his family would hold a funeral on Wednesday and did not wish the presence of any government officials but were calling for a mass popular turnout.

The attack plunged Lebanon into mourning and raised concerns about the stability of the country, which was treading a delicate path between its diverse confessional communities.

Israel, which is still technically at war with Lebanon after ending its 22 year occupation of the south in 2000, also voiced fears of a possible flare-up in violence on its northern border.

“We have to be vigilant because this assassination could cause instability in Lebanon that could be exploited” by anti-Israeli elements, a senior aide to Prime Minister Ariel Sharon said.

He said the attack could have been carried out “either directly by its (Syria’s) secret services, which have long history of this kind of operation, or by terrorist groups linked in one way or another to Syria.”

It came at a time of high political tension in Lebanon and international pressure over Syria’s role ahead of legislative elections planned for May.

The United States angrily condemned the assassination, vowing punitive action and calling for an end to Syria’s military presence, while former colonial power France called for an international inquiry.

“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,” said White House spokesman Scott McClellan.

Washington reached out immediately to its allies, governments in the region, and the UN Security Council to punish those responsible and to push for a Lebanon “free of foreign occupation,” said the spokesman.

In Beirut, protesters tried to set fire to an office of Syria’s ruling Baath Party and took to the streets of Sidon, Hariri’s hometown in south Lebanon where they set tires ablaze.

The Security Council last September adopted Resolution 1559 calling for a halt to foreign interference in Lebanon and a withdrawal of foreign troops.

Hariri, who was born to a poor farmer but rose to became one of the world’s 100 richest people, headed five governments from 1992. But he later became a thorn in the side of Beirut’s political masters in Damascus and resigned as premier in October after disputes with pro-Syrian President Emile Lahoud.

Anti-Syrian opposition leaders demanded a three-day general strike, the resignation of the government and a Syrian troop withdrawal, saying it held the regimes in Beirut and Damascus responsible.

Syria was nevertheless among the first to condemn the attack. “This odious crime is aimed at striking Lebanese national unity and civil peace,” President Bashar al-Assad said.

UN Secretary General Kofi Annan said the attack was from “a chapter in Lebanon’s history” he had hoped was over and warned against further destabilisation.

State-run television said more than 350 kilograms (770 pounds) of explosives were used in the bombing, bringing down concrete walls, leaving a dozen flaming cars and gouging a crater several metres into the road.

Supporters of Hariri gathered outside his west Beirut mansion, weeping and banging their heads in grief.

“Hariri is dead, Lebanon will not survive. It’s going to break apart into sectarian enclaves,” wailed one distraught elderly man referring to the confessional divisions which fuelled the civil war.

Islamist group An-Nosra wal Jihad fi Bilad al-Sham (Victory and Jihad in Greater Syria) claimed responsibility for the bombing and warned of further attacks on “infidels”.

The group, in a videotape shown on Al-Jazeera television, said Ahmed Abu Ades carried out the attack because of Hariri’s ties with the Saudi regime.

Hariri had close business links with the Saudi royal family and was a frequent visitor to the oil-rich Gulf state which has been a key financial backer of Lebanon.