France “condemns the attack with the greatest firmness”, foreign ministry spokesperson Philippe Lalliot said on Tuesday.
“It calls on all Lebanese to work to avoid an escalation of violence and preserve national unity,” he added.
At least 53 people have been wounded, one of the seriously, in the blast that took place when a car bomb went off in a car park in south Beirut.
Some Lebanese Shia start observing Ramadan on Tuesday, while Sunni begin on Wednesday and other Shia on Thursday.
Fallout from the war in Syria has added bitterness to sectarian divisions in Lebanon with the Shia movement Hezbollah supporting Bashar al-Assad’s regime, while many Sunni politicians back the opposition, as does France.