As the showdown entered its fourth week, an army officer at the scene said the high casualties were suffered in clashes on Saturday that were often at close quarters and accompanied by heavy artillery fire from the military.

The army, which has encircled Nahr al-Bared, tried to push into the Palestinian refugee camp in north Lebanon and overrun positions held by Fatah al-Islam militants, which has snipers posted on rooftops.

"Nine soldiers in total were killed in the clashes yesterday as the army advanced on Fatah al-Islam positions inside the camp," the Lebanese army's spokesman said, updating an earlier toll.

Six troops were killed on Saturday and the other three died of their injuries on Sunday, he said. Almost 40 other soldiers were wounded.

Shahine Shahine, spokesman for Fatah al-Islam, told AFP by telephone from inside the battered refugee camp that four of its fighters were killed and another six wounded.

Two Palestinian civilians, whose bodies were evacuated on Sunday, also died in the shelling of the mostly-deserted camp, rescue workers said.

"The soldiers were victims of booby-trapped bomb blasts and grenades thrown at them by Fatah al-Islam," as they tried to storm the militia's positions on the northeastern outskirts of the camp, said an army commander.

The soldiers were "fighting from high-rise to high-rise but encountering fierce resistance from the extremists who have booby-trapped the buildings," the commander said.

The known death toll since the fighting broke out on May 20 in Nahr al-Bared and the nearby port city of Tripoli has now risen to 121, including 56 Lebanese army soldiers and about 50 Islamists.

Lebanese authorities say the fighting was sparked by raids on Fatah al-Islam hideouts in Tripoli following a bank robbery, after which the militants attacked army posts.

Shahine said the shelling on Saturday had been cover for a ground assault but that the attack had been repulsed.