Three men and a woman were killed in renewed clashes between Sunni and Alawite residents of the northern Lebanese town of Tripoli in less than 24 hours, a security source told AFP Monday.

"One civilian was killed and 21 were wounded in clashes late Sunday between the Sunni-majority Bab el-Tabbaneh neighbourhood and the facing Alawite area of Jabal Mohsen," the source said.

Further clashes on Monday left another two men and a woman dead and five people wounded. Those killed on Monday were all in Bab el-Tabbaneh.

The latest confrontations come after a brief lull in the violence between the two sides, after a flare-up last month left 31 people dead and more than 200 wounded.

The violence is tied to the conflict in Syria, where a Sunni-led uprising is fighting to overthrow the regime of President Bashar al-Assad, an Alawite.

The fighting in Tripoli, which has flared sporadically since the beginning of the Syria conflict in March 2011, has largely been confined to Jabal Mohsen and Bab el-Tabbaneh.

But the repercussions of the Syria conflict have also been felt elsewhere in its neighbour Lebanon.

In the southern port city of Sidon, the Sunni imam of a mosque told journalists he had come under fire from a car by gunmen using automatic weapons as he was walking to prayers.

"It is a message because of my support for (Lebanon's Shiite group) Hezbollah and for favouring a political solution in Syria," Sheikh Maher Hammud of Al-Quds mosque said.

And security services reported another attack on a Sunni imam close to Hezbollah, which is an ally of Syrian President Bashar al-Assad's regime.

They said the car of Sheikh Ibrahim Mustafa Breidi came under machinegun attack in Lebanon's eastern Bekaa area and caught fire.