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Amid a sustained army offensive Tuesday, seven Islamic militants have surrendered to a major Palestinian faction in a besieged refugee camp in northern Lebanon — marking the first tangible move by Palestinian factions against the militants.

But other Fatah Islam militants continued to fight and Lebanese troops pounded their hideouts in the Nahr el-Bared refugee camp on the fifth day of an assault aimed at crushing them. Clouds of smoke rose from the camp as artillery struck militant positions.

The seven militants surrender was the first sign that a major faction — in this case the Fatah group of Palestinian President Mahmoud Abbas — responded to calls by Lebanese authorities to actively campaign against the Al Qaeda inspired Fatah Islam since fighting broke out May 20.

It coincided with by Abbas' renewed denunciation of the group and tacit backing of the Lebanese crackdown on militants in Nahr el-Bared.

Fatah Islam has nothing to do with the Palestinians, Abbas said in a speech in the West Bank marking 40 years of Israeli occupation. He accused the militants of "abusing the camps" to carry out attacks against the Lebanese army, and "endangering the lives of Palestinians" there.

The seven Fatah Islam members came over to Fatah positions in the southern parts of Nahr el-Bared, handed over their weapons and pledged to stay out of the fighting, said Fatah commander Maj. Gen. Khaled Aref.

Speaking from his base in the southern Ein el-Hilweh Palestinian refugee camp, Aref told The Associated Press that Fatah was trying to convince Palestinian residents in the camp who previously had sided with the militants to abandon the fight because it was wreaking destruction on their homes.

Major Palestinian factions have been trying to mediate an end to the confrontation. The government wants the militants, estimated at several hundred, to surrender, but Fatah Islam has vowed to fight to death.

Lebanese officials have been urging the Palestinians to help, but factions have been wary of military involvement because of rivalries and concerns that a direct intervention could spark more violence.

Lebanese security officials, speaking on condition of anonymity because they were not authorized to make statements to media, have said that the army had strategically divided Nahr el-Bared into three zones — one under army control, another held by the militants and a third controlled by Palestinian civilians and guerrillas of Fatah and other factions who were refusing the militants sanctuary.

A senior Lebanese military official said Tuesday the army was tightening the noose around the militants, silencing the source of fire and cleaning bomb-rigged buildings. The officer, who spoke on condition of anonymity because he was not authorized to speak to the press, said he not aware if any Fatah Islam militants had surrendered to Lebanese troops.

More than 100 people have been reported killed in the fighting, the worst internal violence since the end of Lebanon's 1975-90 civil war. Of those were 45 soldiers, including 10 who were killed since the military launched its offensive Friday on Nahr el-Bared. Two other soldiers were killed in Ein el-Hilweh, another refugee camp in southern Lebanon, in separate clashes with militants there. About 60 Fatah Islam militants were also reported killed.

At least 20 civilians have been reported dead at Nahr el-Bared, but recent civilian casualties were unknown.

The international Red Cross said Tuesday it managed to send in some medical supplies to the southern part of Nahr el-Bared — the first time since the offensive began. The Red Cross evacuated 12 people, including one who was wounded and a pregnant woman, said spokeswoman Virginia de la Guardia, bringing the total number of evacuated people to 45 in the last two days.

Most of the camp's 31,000 residents have fled to a nearby camp, but about 5,000 civilians remained behind.

The London-based human rights watchdog Amnesty International said it was "greatly concerned" about civilians trapped in Nahr el-Bared who are being exposed to "grave risk."

A visiting U.S. official on Tuesday reiterated U.S. support for Lebanon. Kristen Silverberg, assistant secretary of state for international organizations, said after meeting with Prime Minister Fuad Saniora that the Lebanese "can be proud of the courage and determination" of the army.

The U.S. has airlifted ammunition and supplies to help the Lebanese army in its showdown with Fatah Islam.

U.S. Ambassador Jeffrey Feltman announced later Tuesday that the U.S will contribute $3.5 million to help the Nahr el-Bared's Palestinian refugees. The announcement was made at a meeting between Saniora and the ambassadors of donor countries during which the Lebanese premier asked for assistance, according to a statement by Saniora's office.

Syria, meanwhile, denied links to Fatah Islam as some Lebanese security officials and members of the Lebanese government allege. Foreign Minister Walid Moallem said in Damascus that the group was outlawed in Syria and "24 of its members are held in Syrian jails."

The bombardment of Nahr el-Bared has angered Palestinians in some of Lebanon's 11 other refugee camps and there were fears that fighting could spread. Calm returned Tuesday to Ein el-Hilweh, Lebanon's largest Palestinian refugee camp where Islamic militants sympathizing with Fatah Islam clashed with troops on Sunday and Monday.

Palestinian Islamic factions have set up a security force to prevent further clashes between Jund al-Sham militants and the army.