A powerful explosion in Shi'ite group Hezbollah's southern Beirut stronghold killed three people on Thursday and sent a column of smoke into the sky, a witness said.
Television footage showed the twisted and blackened remains of several cars being doused with hoses by emergency services. The blast also tore off the facades of several nearby buildings.
About 20 people were wounded, the witness said.
The Lebanese capital has been hit by a series of bombs in recent months, including one last week which killed a former minister and political adversary of Hezbollah.
In November, 25 people were killed by suicide bombers at the Iranian embassy in southern Beirut, and explosions have also hit other nearby Hezbollah districts and Sunni mosques in the northern city of Tripoli.
Conflict in neighbouring Syria has polarised Lebanon and ratcheted up sectarian tensions.
Hezbollah has sent fighters to Syria to join the forces of President Bashar al-Assad, who is from the Alawite offshoot of Shi'ite Islam, while Sunni Muslim fighters have gone to Syria to fight for rebels trying to topple him.