The powerful bomb blast took place in front of the five-star hotels St. George and Phoenicia-Intercontinental in the Lebanese capital's famed Corniche overlooking the Mediterranean Sea. The explosion left a 5 meter (15-foot) crater in the street and spread thick dust and ash over the debris.

One of Hariri's senior bodyguards and officials at the American University of Beirut hospital confirmed Hariri's death. The hospital, which said it had seen another nine bodies and more than 100 injured, said Hariri was dead on arrival.

Witnesses reported seeing at least 10 bodies on the scene.

Bystanders and emergency officials rushed to aid the injured, including one man who climbed from a car window ablaze.

Former Economy Minister Basil Fuleihan, riding in the motorcade, was critically wounded, Reuters reported.

It was unclear if the explosives had been packed into a vehicle.

Hariri, 60, a multi-billionaire businessman who resigned from government last October, recently joined calls by the opposition for Syria to quit Lebanon in the run-up to general elections in May, Reuters reported.

Hariri served as prime minister from 1992-98 and again from 2000 until his resignation after parliament amended the Lebanese constitution to extend Syrian-backed President Emile Lahoud's term by three years. Lahoud had been set to leave office last November. (Hariri profile)

At least six fires were burning in the immediate aftermath of the blast, which took place at about 1 p.m. (1100 GMT).

Several of the vehicles from Hariri's convoy were torn apart and set on fire despite their armor plating, Reuters reported.

Heavily armed security forces cordoned off the area with yellow tape as rescue workers and investigators combed the scene apparently looking for casualties or clues to what caused the huge explosion.