Thousands of people fled a crowded refugee camp Tuesday night during a lull in three straight days of clashes between Lebanese troops and Islamic militants holed up inside.

AP Television News video from the Nahr el-Bared refugee camp showed women clutching children and piling up in pickup trucks, some waving white flags, as they tried to leave the partially destroyed camp.

Others fled on foot, and ambulances could be seen evacuating the wounded.

U.N. relief officials in another camp located a few miles to the south of Tripoli said they expected 10,000 Palestinian refugees from Nahr el-Bared to arrive through the night.

Refugees from Nahr el-Bared were seen raising white towels from windows and even waving white plastic bags. Boys carried babies, and a young boy and a woman helped an elderly woman, hurriedly walking on the side of the road as cars sped past carrying more refugees.

Many of the packed cars driving out had their windows blasted from the fighting.

Earlier, artillery and machine gun fire echoed around the camp, as the Lebanese government ordered the army to finish off the Fatah Islam militants.

Black smoke billowed from the area after artillery and machine gun exchanges at the Nahr el-Bared camp on the outskirts of the port city of Tripoli.

A U.N. convoy carrying relief supplies was hit, possibly resulting in casualties, a relief official said.

The official from the U.N. Relief and Works Agency said a pickup truck and a water tanker were caught between the lines of the militant Fatah Islam fighters and the Lebanese army, which fired at the convoy.

"The army hit the place where the pickup truck and the tanker were. The army knew we were there and emptying our goods," the U.N. relief official told The Associated Press by telephone from the entrance of the camp.

"There may have been some casualties, at least one," the official said, speaking on condition of anonymity because he was not authorized to talk to the media.

Inside the city itself, security forces moved in against a suspected Fatah Islam hideout in an apartment building, witnesses said.

Shots rang out on Mitein Street at midmorning as security forces, after receiving a tip about armed men in an apartment, raided the building using tear gas and leaving it gutted. Apparently no one was caught.

The developments reflected the government's determination to pursue the Islamic militants who have staged attacks on Lebanese troops since Sunday, killing 29 soldiers. Some 20 militants have also been killed, as well as an undetermined number of civilians.

Lebanon's Cabinet late Monday authorized the army to step up its campaign and "end the terrorist phenomenon that is alien to the values and nature of the Palestinian people," Information Minister Ghazi Aridi said.

Major Palestinian faction leaders met with Prime Minister Fuad Saniora for the second time in as many days. European Union foreign policy chief Javier Solana arrived Tuesday in Beirut to discuss the latest crisis gripping Lebanon.

A spokesman for Fatah Islam, Abu Salim Taha, said the group managed to repulse several attempts by Lebanese troops to advance on their positions inside the camp.

"The shelling is heavy, not only on our positions, but also on children and women. Destruction is all over," he said. Speaking to The Associated Press by telephone from the camp, he denied his group was behind bomb blasts in Beirut on Sunday and Monday night.

The latest fighting has raised fears that Lebanon's worst internal violence since the 1975-1990 civil war could spread in a country with an uneasy balancing act among various sects and factions.