The National News Agency said smoke was seen billowing from the southern suburbs of Beirut. The Daily Star newspaper said Thursday at least 10 people were reported killed in the bombing.
More than a dozen members of the Lebanese military were killed during June fighting with supporters of a Sunni cleric critical of Hezbollah. A car bomb exploded July in a Hezbollah stronghold in Beirut, leaving more than 50 people injured.
The bombing Thursday followed a statement from Hezbollah Secretary-General Hassan Nasrallah claiming responsibility for a border incident involving Israeli soldiers.
Four soldiers were wounded last week by an explosion after they crossed a few hundred feet into Lebanese territory near a U.N. observation post.
The U.N. Interim Force in Lebanon said it was frustrated by the Israeli incursion, adding it was investigating the source of the explosion.
"Hezbollah had prior information that two Israeli units ... were planning to infiltrate Lebanon so we planted the explosives," Nasrallah said Wednesday. "The operation was deliberate and not an accident nor was it the result of a landmine left over from the Israeli occupation of Lebanon."
Lebanon has been on edge since Hezbollah acknowledged it was fighting rebel forces in neighboring Syria.
The European Union recently listed Hezbollah's military wing as a terrorist organization. The Shiite organization is member of the March 8 political coalition.