Hundreds of civilians fled from areas where the fighting broke out
At least four people have been killed as sectarian clashes continued for a second day in north Lebanon, bringing the death toll to eight, police said.
Fighting on the outskirts of Tripoli has pitted Sunnis from the anti-Syrian faction against pro-Syrian Alawites.
Several homes and a petrol station were set ablaze and people fled the area.
The violence comes despite a political accord which led to the election of a president and moves towards forming a government of national unity.
Western-backed anti-Syrian Prime Minister Fouad Siniora and pro-Syrian parties led by Hezbollah have so far failed to reach agreement on the make-up of the new government.
Gunmen traded fire between the mainly Sunni Muslim Bab Tibbaneh district and the Alawite Jabal Mohsen area.
They fired machineguns, grenades and mortars, driving hundreds of civilians from the area.
One of the fatalities on Monday was a 55-year-old man killed by a stray bullet as he drove along the main highway linking Tripoli with Syria. Two other people died of wounds sustained on Sunday.
Large numbers of Lebanese army troops could be seen deploying in an area close to the fighting, which then subsided on Monday afternoon.
The two sides agreed a ceasefire on Sunday but it quickly broke down in further clashes.
Mr Siniora condemned the fighting as he attended a donors' conference in Vienna to collect funds to rebuild the destroyed Nahr al-Bared Palestinian refugee camp which lies to the north of Tripoli.
"We really condemn every use of weapons against these civilians and the use of weapons inside the country," he said.