NAHR AL-BARED, Lebanon - Palestinian groups and aid workers said on Wednesday they are working to protect hundreds of refugees believed to be trapped by deadly fighting around a camp in north Lebanon and running out of supplies.

Lebanese security services, meanwhile, said three Islamist fighters were killed as the army repulsed an attack late Tuesday inside the bombed-out Nahr al-Bared refugee camp.

A correspondent reported renewed exchanges of gunfire on Wednesday between troops and Fatah al-Islam extremists around the camp where electricity and running water have been cut, amid sporadic shelling by the military.

Bilal Aslan, a senior official of the mainstream Palestinian faction Fatah, told AFP from inside the camp that a "security cordon" has been set up for civilians in the heart of the southern sector of Nahr al-Bared.

Fatah al-Islam was being kept out by force if necessary, he said, adding however that an occasional round of shellfire was crashing inside the zone, without reporting any civilian casualties.

The Arab Islamists, some of whom have their families with them, have suffered "a lot of dead or wounded, and their number has gone down a lot but we don't know how many are left," Aslan said.

The army, meanwhile, has tightened the net around Nahr al-Bared after Fatah al-Islam used the entry of aid convoys to attack army vehicles, he said.

Samir Libani, an official of the Popular Front for the Liberation of Palestine, estimated about 800 civilians remain in the camp and warned they are running out of food and water.

A source with the security services said the bodies of three militants were evacuated by civil defence workers after the attack on the army in Nahr al-Bared, scene of a six-week showdown between troops and the Al-Qaeda-inspired extremists.

"There was an infiltration attempt. The army fired back and the militants pulled back to positions deep inside the camp, as usual. They have no fixed posts," an army spokesman told AFP, without confirming the casualties.

Fatah al-Islam, which had spokesmen contactable by mobile phone in the early stages of the battle, was again unreachable on Wednesday. Their phone lines have apparently been cut off.

The International Committee of the Red Cross warned of the deteriorating humanitarian situation inside the camp.

An ICRC spokeswoman, Virginia de la Guardia, said relief workers had not been able to deliver food and water supplies to the camp since June 20, with trapped residents running out of supplies.

"Discussions are continuing with the army" for access, she said.

The last food rations which entered the camp amounted to 760 kilogrammes (1,670 pounds), enough for just over 100 people for two weeks, said the delegate of the ICRC, which has been coordinating relief.

The army has been battling the Islamists boxed inside the camp near the Mediterranean port city of Tripoli since May 20.

As aid workers continue to seek access to trapped civilians, Palestinian factions have struggled to agree on the mandate of a proposed force to end the deadly showdown in the besieged camp.

In the absence of reliable figures, hundreds of Nahr al-Bared's original population of 31,000 are believed to remain inside the camp. The vast majority took advantage of lulls in the fighting to flee.

According to a count compiled from official figures and security sources, the battle has now claimed at least 173 lives, including 85 soldiers, in and around Nahr al-Bared. The toll does not include the corpses of fighters abandoned in the camp. -AFP