Lebanese Prime Minister Tammam Salam held an emergency meeting with his security cabinet and military chiefs on Friday as the nation mourned 44 people killed in a double suicide bombing claimed by Islamic State.
The blasts late on Thursday hit a residential and commercial area in a southern suburb of Beirut, a stronghold of Shi'ite Muslim group Hezbollah, in the latest spillover of violence from the war in neighboring Syria.
The first attacks in more than a year on a Hezbollah bastion inside Lebanon came at time when the group is stepping up its involvement in Syria's civil war, now in its fifth year.
Iran-backed Hezbollah has sent troops over the border to support Syrian President Bashar Assad against Sunni Muslim insurgent groups including Islamic State.
Lebanon is also suffering from its own political crisis in which disputes between parties, factions and sects have stopped the government taking basic decisions and left the country without a president for 17 months.
The army established a heavy security presence around the scene of the blast, which on Friday was still littered with debris, damaged cars and motorbikes and shattered glass.
Medical sources raised the death toll on Friday from 43 to 44, with more than 200 people wounded.
Funerals were held in Beirut for several of the victims later in the day, with coffins draped in the flags of Hezbollah and Amal, another Shi'ite movement.
Defense Minister Samir Moqbel said the armed forces were on high alert across the country, and trying their best to keep a fragile calm.
"To tell you the security forces can control things like that 100 percent of the time, I'd be lying," he said. "We're doing our best in coordination with all the parties on the ground."