The U.N. World Food Program said that Sudanese security forces surrounded and removed some refugees from two camps near Nyala before dawn, while in a third camp Sudanese forces fired shots in the air and tear gas to disperse crowds.
The WFP fears the government may start forcing people from the camps back to their home villages, where there is less protection from militias known as Janjaweed that have been attacking towns, said WFP spokeswoman Christiane Berthiaume. Sudan's government is accused of backing the Janjaweed in a campaign of violence -- including rapes, killings and the burning of villages -- to help put down a 19-month rebellion by non-Arab-African groups. The government denies backing the militias.
The WFP said it was forced to evacuate 88 aid workers from those areas due to deteriorating security conditions.
The camps in Golu, Zaleinge and Nertetie were closed off at 3 a.m. without any warning, and agencies have been denied access to the camps ever since, Berthiaume told the Associated Press.
At least 160,000 refugees in western Darfur cannot be reached by road "because of insecurity," she added.
Violence has driven more than 1.5 million of Darfur's people from their homes, and at least 70,000 have died, mostly through disease and hunger, in what the United Nations calls the world's worst humanitarian crisis.
Barry Came, the WFP's spokesman in Khartoum, told Reuters that tensions in the area had risen since African Union monitors reported that the rebel Sudan Liberation Army had taken 11 Arab civilians hostage near Zaleinge. The rebels have claimed Janjaweed ordered 30 ethnic Africans from a bus on Sunday and shot them to death, the AP reported.
The Sudanese government on Tuesday denied that any army or police forces were surrounding the camps, and blamed the rebels for any deteriorating security.
"There is no siege," Sudanese Humanitarian Affairs Minister Ibrahim Hamid told the AP. "It is not true that the government was telling organizations to pull out of the area, and the areas are not besieged."
Hamid said angry Arab tribesmen gathered in the area after the kidnapping of 18 of their men by Darfur rebels. "The African Union has been alerted and they said they would bring those abducted out of the mountainous areas of Zaleinge," he said.
Foreign Minister Mustafa Osman Ismail told Reuters, "If there is any increase in insecurity it is because of rebel activities."
Despite the ongoing tension, peace talks between the government and two rebel groups continued in the Nigerian capital, Abuja. African Union officials on Monday presented the final draft of a compromise security agreement, which the rebels have cautiously praised.