Lebanon's army launched heavy artillery barrages into a besieged Palestinian refugee camp in north Lebanon on Tuesday in its continued struggle to overtake Islamic militants holed up inside.

The renewed fighting comes a day after a mortar shell fired by Fatah Islam militants inside the Nahr el-Bared camp killed two Lebanese Red Cross workers and injured a third.

A senior military official said Tuesday that the army was reinforcing its positions and "tightening the noose" on the militants inside the camp. The official, speaking on customary condition of anonymity because he was not authorized to give official press statements, again urged Fatah Islam fighters to turn themselves in.

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The fighting in the Nahr el-Bared camp which began on May 20 has dragged on for more than three weeks with no imminent end in sight.

The army announced Tuesday that three of its soldiers were killed in Monday's fighting, bringing the total of soldiers killed in the Nahr el-Bared fighting to 60.

Two more soldiers were killed in last week's clashes with Jund al-Sham militants in another Palestinian refugee camp, the Ein el-Hilweh in southern Lebanon.

In addition to the Red Cross and army deaths, a Muslims sheik trying to mediate an end to the fighting between the Lebanese army and the militants was lightly wounded Monday as he left the camp in a Palestinian Red Crescent vehicle.

Sheik Mohammed Haj said he met inside the camp with Shahin Shahin, the alleged military commander of Fatah Islam, to discuss an end to the fighting. "The meeting was positive, he showed flexibility during the talks," Haj told The Associated Press by telephone from his hospital bed in Tripoli but refused to provide more details.

A security official said Monday that troops had destroyed the residence and headquarters of Fatah Islam leader Shaker Youssef al-Absi. It was not clear if al-Absi, who is said to have several residences and offices, was there during the attack.

More than 140 people in total, including at least 60 Fatah Islam militants, 20 civilians and the two Red Cross workers, have been reported killed in the fighting in northern Lebanon — the worst internal violence to engulf the trouble-plagued country since the 1975-90 civil war.

"Nahr el-Bared turns into a hell for army," read the headline of the leftist daily As-Safir Tuesday.

The United Nations Security Council gave strong backing to the Lebanese government's fight against militants.

"The council condemns the ongoing criminal and terrorist acts in Lebanon, including those perpetrated by Fatah al-Islam, and fully supports the efforts carried out by the Lebanese government and army to ensure security and stability throughout Lebanon," the council's presidential statement said after a meeting Monday.

In a sign that Nahr el-Bared's siege was being followed by other militants across the region, a Syrian Al Qaeda-inspired group on Tuesday warned it would carry out attacks, "kidnapping, shooting and chopping of heads" of Lebanese in Syria if the Lebanese army doesn't stop bombarding Fatah Islam.

The group known as "Tawhid and Jihad in Syria" pledged support for Fatah Islam, according to a statement posted on a Web forum commonly used by militants.

"We warn the Lebanese government that its vital interests, officials and sons living in Syria will be moving targets for us if it does not lift its siege of the camp," it said.

The group in Syria first became known in November, when its former leader Omar Abdullah clashed with Syrian security forces and blew himself up on the border with Lebanon. Its name in Arabic stands for "monotheism and holy war," though the group's actual links to Usama bin Laden are not clear.

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