Pro-government leaders have called on hundreds of thousands of supporters to converge Thursday on Martyr's Square in central Beirut, near the beachfront site of the car bombing that killed Hariri and 22 others on February 14, 2005.

The rally was to be held on the same day that the Shiite militant group Hezbollah, leader of the Iranian- and Syrian-backed opposition, was to bury one of its top commanders killed on Tuesday in Syria, in a car bombing blamed on Israel.

The Hariri anniversary protest comes amid high tension in Lebanon which has been without a president since November, in its worst political crisis since the end of the 1975-1990 civil war.

Street clashes between militants from the pro- and anti-Syrian camps and mudslinging among rival politicians have raised fears of civil strife, prompting the security forces to take a series of preventive measures.

Scooters have been banned from travelling in and around Beirut on Thursday and civilians have been ordered not to carry weapons through Friday, even licenced ones.

An army spokesman told AFP that "troops will be deployed throughout the capital to ensure security".

Concern of unrest have also prompted foreign embassies in Lebanon to urge their citizens to observe extreme caution and avoid travel in the capital Beirut on Thursday.

"The US embassy encourages American citizens in Lebanon to limit all but essential travel on February 13 and 14," a statement said. "Americans that absolutely need to travel on these days should maintain a heightened level of awareness."

Vans mounted with loudspeakers have meanwhile criss-crossed Beirut and other cities around the country urging people to join the rally, while messages calling for mass participation were put up everywhere.

"In 2005 you took to the streets to force them out. In 2008 you must do the same so that they don't come back," read the messages on large billboards in and around Beirut, referring to Syrian troops

Hariri's killing sparked international outrage and was blamed on Syria, which has denied any involvement.

But two months after the car bombing, Syria ended nearly three decades of military domination over Lebanon and withdrew its troops from the country.

The pullout came a month after the ruling majority held a massive rally on March 14 to press for an international inquiry into the assassination and demand the Syrian withdrawal.

Since Hariri's death, nine politicians, journalists and other figures have been killed in similar attacks.

One of the pillars of the ruling majority, Walid Jumblatt, said on Tuesday that his camp could not co-exist with the Hezbollah-led opposition and demanded they part ways.

"I want an amicable divorce," Jumblatt said.

"Let them keep their weapons, their culture, their media, but they should leave us alone to live in peace," he added, accusing the Shiite Muslim militant group of forming "a state within a state" and heeding Syria and Iran.

Opposition figures have also ratcheted up the rhetoric warning that their patience has its limits.

The standoff between the two camps has prevented parliament from electing a new president to replace pro-Syrian Emile Lahoud, whose terms ended in November, with 14 sessions scrapped since September.