Libya's interim government has asked the United Nations for fuel for ambulances to evacuate wounded from the besieged city of Sirte, a UN source in Libya said on Thursday.
Meanwhile desperate civilians were fleeing the coastal city, held by fighters loyal to deposed leader Muammar Gaddafi, before dawn when pro-Gaddafi forces start guarding checkpoints, the source told Reuters.
The United Nations is sending trucks of clean drinking water for the increasing flow of civilians crammed into vehicles on the road from Sirte, heading either towards Benghazi in the west or Misrata in the east, he said.
But fighting around the city, Gaddafi's hometown, and continuing insecurity around the Bani Walid area, the other final loyalist hold-out, are preventing the world body from deploying aid workers inside them, he said.
"There are two places we'd really like access to, Sirte and Ben Walid because of concern on the impact of conflict on the civilian population," the UN source in Tripoli, speaking by telephone on condition of anonymity, told Reuters in Geneva.
The United Nations has stocks of food and water in both Benghazi and Misrata for the newly displaced but many are taken by villagers and local councils on the way, he said.
"We know battles are raging and we would like access to Sirte but nobody has been able to enter the city," the UN source said. "We've heard there are a lot of casualties and wounded are being sent towards Misrata.
"We've received a request for fuel for ambulances from the NTC to move wounded people from the frontlines westward. That gives an indication that maybe logistics are not working as effectively as they could and we need to step in with support," he added.
UN officials do not have any direct contact with pro-Gaddafi forces holed up in Sirte, where both sides accuse the other of cutting off water and electricity, he said.
"We had reports two days ago that up to 250 vehicles per day are leaving westward, early in the morning before checkpoints are properly manned by pro-Gaddafi forces."
Thousands of civilians are streaming out of the besieged town, where a humanitarian disaster looms amid rising casualties and shrinking supplies of water, electricity and food, major aid agencies said on Wednesday.
"We are focusing primarily on the displaced because our capacity is not very strong. The main challenge is to find where they are, what the numbers are and what their needs are," the UN. source said.
Last week the UN had reports that up to 35,000 people had fled Bani Walid, about half the population, reaching Tnine and Shmeikh, he said.
"We could not reach those two places, they were beyond the perimeter of our security clearance," he said, adding that they were insecure areas but not under the control of pro-Gaddafi forces.
Since then, many of the displaced people are believed to have moved on, he said, most likely to Gharyan and Tripoli.
"We are also concerned about Sabha but we need an extra team. We hope to get there sometime next week," the UN source said, referring to a southern town.