At least two people were killed and 15 wounded by a huge bomb that exploded in a street in central Beirut on Friday, witnesses and a security source said.
A Reuters reporter saw at least one body at the scene and the security source confirmed two dead.
It was not immediately clear if the explosion targeted any political figure in Lebanon's divided community but it occurred at a time of heightened tension between Lebanese factions on opposite sides of the Syria conflict.
Ambulances rushed to the scene in the Ashafriyeh district, a mostly Christian area, as smoke rose from the area.
Several cars were set on fire by the explosion and the front of a multi-story building was badly damaged.
Residents ran about in panic looking for relatives while others helped carry the wounded to ambulances.
Security forces blanketed the area.
The war in neighboring Syria has pitted mostly Sunni insurgents against President Bashar al-Assad, who is from the Awali sect linked to Shia Islam.
The last bombing in Beirut was in 2008 when three people were killed in an explosion which damaged a US diplomatic car.
However fighting had broken out this year between supporters and opponents of Assad in the northern city of Tripoli.
