The United Nations has urged Sudanese authorities to allow humanitarian organisations access to a Darfur refugee camp, which was closed to aid agencies more than a week ago due to an outbreak of violence.

Martin Nesirky, a UN spokesman, said on Tuesday that about 50,000 people are believed to still be in the Kalma camp in southern Darfur, cut off from humanitarian assistance.

"We are concerned about the shortages of food and fuel. Deliveries have stopped and fuel for water pumps has run out. And so, obviously, sanitation is a major concern, because it's the middle of the rainy season," he said.

Several thousand people who fled the camp have also taken refuge outside a community police centre run by joint UN-African Union peacekeeping forces (Unamid), Nesirky said.

"The government must resume full humanitarian access to Kalma and to surrounding areas where displaced people have fled."

Last week, at least five people died and thousands fled the camp following demonstrations against peace talks that turned deadly, according to the UN Office for the Coordination of Humanitarian Affairs in Darfur.

'High alert'

Nesirky said there have been recent reports of sporadic firing in the camp, but added that the commander of Unamid visited the camp over the weekend and the peacekeeping force, now on high alert, has stepped up patrols in and around Kalma.

Ibrahim Gambari, the top Unami representative in Darfur, also continues to engage the government "at all levels to peacefully resolve the situation" and ensure the protection of all displaced people and civilians, Nesirky said.

At a briefing late last month, the UN Security Council was told of rising tensions and clashes in Kalma between supporters and opponents of the peace talks being held in Doha, the Qatari capital.

The Doha talks are the first between Sudanese government officials and Darfur rebels in nearly two years, after comprehensive peace talks broke down in late 2007.

The security council has condemned targeted killings and urged all parties to join the peace process and refrain from violence.