Despite a truce called a day before in Lebanon, sounds of gunfire and mortar fire could be heard Wednesday coming the refugee camp that has been the scene of battles between the Lebanese army and an Al Qaeda-linked group.

Mortars rounds were heard exploding and small-arms fire and tracer fire were seen south of the camp after nightfall.

A FOX News reporter had witnessed Lebanese army troops shoring up positions inside the Palestinian refugee camp of Nahr el-Bared throughout the day.

Hundreds of Palestinian civilians carrying their belongings in plastic bags were trickling out of a besieged refugee camp earlier Wednesday, taking advantage of the temporary pause in fighting.

About 15,000 — nearly half the camp's residents — fled Tuesday night and another 1,000 left Wednesday, officials said. Those fleeing reported bodies littering Nahr el-Bared's streets and scenes of blasted buildings and destruction. U.N. officials said the bodies of at least 20 civilians have been retrieved from the camp.

Meanwhile, Lebanese military officials said the body of the second-in-command of the Fatah Islam militant group was retrieved Wednesday near the camp in Tripoli.

The officials, speaking on condition of anonymity because they were not authorized to talk to the media, said that the Lebanese Civil Defense personnel uncovered the body of Abu Madyan in the area of Abde, just north of the Nahr al-Bared camp.

Abu Madyan was killed on Monday during battles between his group and the Lebanese army. He is the highest ranking member of the group to be killed since the battles began near the camp Sunday.

The Lebanese government has said it's determined to uproot Fatah Islam, and on Wednesday, the army reinforced its positions around Nahr el-Bared.

A militant who identified himself as Fatah Islam's deputy leader told The Associated Press the group would never surrender and vowed to fight to the death if attacked.

"We are ready to enter into a permanent cease-fire on condition we stay, military action against us is halted and life is allowed to return to normal in the camp," said the militant, who goes by the name Abu Hureira.

He sat on the floor of a dimly lit building basement deep inside the camp, the entrance packed with canned food and fruit.

"If they enter, we are ready. They can try but they won't be able to. They will face a massacre," he said, speaking with a Lebanese Arabic accent.

Occasional gunshots were heard overnight, witnesses said. But the relative lull in fighting gave residents the opportunity to flee the battle-scared Nahr el-Bared.

"It's very tense," said Rania Mustafa, 23, holding the hand of a child and carrying a baby in her arms. Other women carrying children were seen stepping over broken glass and garbage and walking around wrecked cars. A loose cow roamed on another street.

Many of the fleeing refugees have moved to a nearby Palestinian refugee camp at Beddawi, where U.N. relief officials and local provided shelter, mattresses, food and water.

Twenty-nine soldiers and at least 20 militants have been killed since the battle began Sunday in the heaviest internal fighting in Lebanon since the 1975-90 civil war.

Taleb al-Salhani, a security officer with the U.N. agency for Palestinian refugees, said the bodies of 20 civilians — men, women and children — have been retrieved from the camp. The total number of civilian casualties remained unknown.

The fighting raises the prospect that parts of Lebanon could become havens for terrorists training to attack the West — similar to lawless regions in Iraq and Afghanistan.

The small country is home to some 215,000 Palestinian refugees who live in a dozen camps rife with armed groups and Islamic extremists, including Fatah Islam.

A senior official of the radical Palestinian faction Islamic Jihad warned that a Lebanese army assault at Nahr el-Bared would trigger violence in other camps.

A group of Palestinians in Lebanon's largest refugee camp, Ein el-Hilweh in the south, said they will form "Jihadi groups" to fight alongside Fatah Islam, according to an Internet statement posted Wednesday. The claim could not be independently verified, but it was posted on a Web site commonly used by Islamic extremists.

"Your brothers announce structuring Jihadi groups in Ein el-Hilweh to respond to the dire atrocities in Nahr el-Bared refugee camp," the statement read.

Fatah Islam's leader, Palestinian Shaker al-Absi, has been linked to the former head of Al Qaeda in Iraq, Abu Musab al-Zarqawi, and is believed to have recruited about 100 fighters, including militants from Saudi Arabia, Yemen and other Arab countries.

The military's attack on the camp also has raised fears the fighting could destabilize Lebanon's uneasy balance among its many religious sects and factions. The U.S.-backed government already faces a domestic political crisis, with the Iranian- and Syrian-backed Hezbollah militant group campaigning for its removal.

But so far, the opposition has supported the assault. The Shiite Muslims of Hezbollah deeply oppose Sunni militant groups like Fatah Islam, and the movement issued a statement stressing the military's duty to safeguard the country.

The Bush administration also has backed Lebanese Prime Minister Fuad Saniora and has hinted that it suspected Syria's involvement. The White House has said the militants wanted to distract international attention from an effort at the U.N. to establish a tribunal to try suspects in the 2005 assassination of former Lebanese Prime Minister Rafik Hariri.

Lebanese security officials accuse Syria of using Fatah Islam to destabilize Lebanon, a charge Damascus denies. Syria controlled Lebanon for decades until it was forced to withdraw its troops after Hariri's assassination.

FOX News' Greg Palkot and the Associated Press contributed to this report.