Four Lebanese soldiers have been killed in renewed clashes with Islamist militants entrenched in a Palestinian refugee camp, officials say.

The men were killed near the Nahr al-Bared camp, on the outskirts of the northern city of Tripoli.

The fighting between the Lebanese army and the Fatah al-Islam group is now in its fourth week.

More than 130 people have been killed since violence broke out on 20 May, in the worst fighting since the civil war.

The exact circumstances of the soldiers' deaths were not immediately clear but the AFP news agency reports that the soldiers came across booby-trap bombs on the edge of the camp.

Plumes of black smoke could be seen rising from the camp as the sounds of gun and tank fire rang out, security officials said.

Most of the camp's 40,000 residents have already fled to the nearby Beddawi camp.

The Fatah al-Islam group emerged late last year when its leader, well-known Palestinian militant Shakir al-Abssi, and some 200 fighters separated from the pro-Syrian Fatah al-Intifada group.

PHOTO CAPTION

An explosion strikes the Nahr el-Bared refugee camp near Tripoli, Lebanon