Overnight clashes in Beirut between Sunni and Shiite gunmen have wounded at least six people, Lebanese officials said.
Troops managed to separate the gunmen and calm returned to the two neighbourhoods in the capital where fighting had erupted.
The officials also reported heavy overnight clashes in the northern city of Tripoli.
Lebanon has been boiling since Friday after an anti-Syrian top intelligence official was assassinated in a Beirut car bombing.
The assassination has threatened to shatter the country's fragile political balance.
Many politicians have blamed Syria for the killing and angry protesters tried to storm the government palace after Brigadier General Wissam al-Hassan's funeral on Sunday.