Thousands of Palestinians are leaving a refugee camp in northern Lebanon after three days of fighting between Fatah al-Islam and the Lebanese army.

"Nahr al-Bared residents have taken advantage of the truce in the fighting to escape the besieged and heavily bombarded camp," Hajj Rifaat, an official from the mainstream Fatah faction, said.

"Thousands of refugees - men, women and children - started fleeing on foot or by car ... to take shelter in the nearby Beddawi camp," he said on Tuesday.

Residents took advantage after Fatah al-Islam said that it was ready to "respect a ceasefire" to help the residents of the camp.

Al Jazeera's Zeina Khodr said: "Busloads of civilians are being evacuated ... some of the people who are fleeing are injured and require urgent medical treatment. They are being taken to hospitals into the northern city of Tripoli."

UN officials in the Beddawi camp about 10km away said they expected 10,000 refugees to arrive through the night.

Ibrahim Issa Dawoud, who left the camp with his wife and six children, said: "We thought this was our last chance because they will bulldoze the camp. That is why we took the risk and fled."

The truce appeared to have collapsed when a UN aid convoy that had been allowed into the Nahr al-Bared came under fire.

Four Palestinian civilians were killed and at least six critically injured before the trucks were forced to pull out.

The convoy had waited for hours outside the camp near Tripoli as humanitarian organisations warned of disaster if food, water and medicines did not reach the refugees soon.

Humanitarian concerns

The 40,000 Palestinians living in Nahr al-Bared are reportedly running out of supplies as the refugee camp remains virtually under siege.

"There is very clearly a big demand for assistance in the camp at the moment. Water is a major issue, food and medical supplies will be a major issue very soon," Sven Berthelsen of UNRWA, the agency that cares for Palestinian refugees, told Al Jazeera.     

"We are very concerned about the potential spread of disease as sanitational systems are not functioning problems and water supplies are not adequate."

He added that the agency would try again on Wednesday to get aid to the people trapped in the camp.

Medical sources have been calling for a halt to the fighting so they can reach the dead and wounded on the streets.

Omar Keenan, a doctor in one of the camp's medical centres, told Al Jazeera the situation was a "disaster".

"There are severe casualties. We are in need of blood, our blood bank is empty. We are performing operations on the floor. These medical centres have come under fire and people are crying out for help. We have no ability to cope. The number of casualties is in the hundreds.

More than 80 people since Sunday have been killed in the country's worst internal violence since the 1975-1990 civil war.

PHOTO CAPTION

Palestinian children look out from their window in Nahr al-Bared refugee camp in northern Lebanon May 22, 2007. (Reuters)

Al-Jazeera (summarized)