UNITED NATIONS, April 29 (Xinhua) -- Approximately 50,000 civilians are still trapped with Sri Lankan rebels on a tiny sliver of beach in the northeast of the island country, the top UN humanitarian official said here Wednesday after returning from a two-day trip.

    "Tens of thousands are in what we no longer call the safe zone or the no-fire zone, but what is now the combat zone," UN Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator John Holmes told a press conference here. "They are still in great danger" and it is "a top priority" to get them out.

    Ideally, Holmes said the United Nations would like to evacuate the remaining civilians trapped by the government's offensive against the Liberation Tigers of Tamil Eelam (LTTE), but that would require a cease-fire, which the government has argued would benefit the rebels. Government leaders also told Holmes that it would "not be safe nor appropriate," he recounted.

    The International Committee of the Red Cross is able to bring 30 tons of food by boat every other day to the trapped civilians but it "doesn't go very far," said Holmes.

    On Wednesday, top envoys of France and the United Kingdom, two of the United Nations Security Council permanent members, were also unable to secure an immediate truce during their meeting with Sri Lanka's leaders. However, they did receive yet another pledge that humanitarian workers would be granted greater access to refugee Tamils.

    The fact that aid workers have not been allowed to see or speak with refuges immediately after they leave the combat zone has allowed for allegations of abuse to run rampant in the government camps, Holmes said.

    Because families fleeing the combat zone are often separated into different government camps, it is giving rise to stories of abductions and human rights abuses by Sri Lanka's military. If aid workers had improved access to the civilians, they would be able confirm or disprove the allegations, said Holmes.

    Currently, there are 175,000 people living in 38 camps in and around the towns of Vavuniya, Jaffna and Trincomalee. While their situation is "extremely poor and worrying," Holmes said nongovernmental organizations have done a "heroic job" providing shelters. In four days, aid workers assembled 4,500 tents -- a record perhaps.

    Meanwhile, 13 UN staff members continue to be held in the government camps against their will. Holmes called it "unacceptable" that the Sri Lankan government had still not allowed them free movement after repeated requests.

    Last week, Sri Lankan Ambassador to the UN G.S. Palihakkara told reporters that the 13 UN staff members are going through a screening process, which is "taking a long time." He expressed his hopes that UN personnel would be able to leave the camps as soon as possible

    Holmes once again urged the Sri Lankan government to exercise restraint, particularly of heavy weapons which they promised not to use early this week. He also hoped the LTTE would let civilians go and lay down their arms to prevent the further loss of lives, although he reasoned this to be unlikely.