A police spokesman told Alalam Satellite TV that Parliament member Antoine Ghanem was among the six killed by the explosion in the Sin el-Fil neighborhood outside Beirut.
An unknown number also were hurt in the blast, near the home of former President Amin Gemayel.
The deadly explosion comes a week before the Lebanese Parliament is to meet to determine who will replace President Emile Lahoud and several months after Parliament member Walid Eido was killed in a Beirut bombing that killed nine others.
Lebanon is mired in a political battle that began with the death of former Lebanese Prime Minister Rafiq Hariri in February 2005.
Alalam said if the warring sides in the political conflict cannot reach agreement regarding the nation's next leader, two rival governments could be created.