BEIRUT, Lebanon - Lebanon plunged into deep mourning and put its army on alert against violence today, a day after a massive bomb killed former Prime Minister Rafik Hariri and raised fears that Lebanon might revert to the political violence of its 1975-90 civil war.

Schools, banks and shops were closed and the streets of the capital were virtually empty today as Lebanon started three days of mourning. Soldiers were deployed at some intersections, the armed forces were put on full alert and leave for troops was canceled.

Police raised the toll from Monday's bombing in downtown Beirut by one to 14 dead and about 120 injured.

TV stations and radios played somber music or readings from the Quran, Islam's holy book, as the country prepared to bury Hariri in a funeral on Wednesday at a downtown Beirut mosque.

At the site of the bombing, troops clamped a cordon around the area. Explosive experts combed rooftops and the street in search of evidence that could reveal what caused the explosion. Security officials have not confirmed initial reports that said the blast was caused by a car bomb.

It was unclear if the assassination would delay parliamentary elections that are expected in April and May. In the morning before his death, Hariri had attended a parliamentary debate on a bill to redefine the electoral districts.

The dead included Hariri and seven of his bodyguards, crushed and burned in their heavily armored cars by the force of the blast, which police estimated at about 660 pounds of TNT.

Condemnation and expressions of shock came from around the Arab world and beyond. Lebanon's opposition accused Syria, the main power broker in this country, and its allied Lebanese government of being behind the assassination and demanded the Syrian army withdraw from Lebanon. Syria condemned the killing and dismissed the claims.

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.