N'Djamena: Gunmen in eastern Chad have prevented the United Nations from moving newly-arrived refugees from Sudan's Darfur region away from a volatile border area and into camps, the world body said on Friday.

The office of the United Nations High Commissioner for Refugees (UNHCR) said armed men stopped a group of families from boarding UN trucks in the Birak border area this week and other refugees due to be collected had moved away for fear of attacks by Sudanese militias.

"We are very disturbed that in eastern Chad on Tuesday our efforts to move traumatised, newly-arrived refugees from West Darfur away from the volatile border to camps was blocked by the presence of unknown armed elements," UNHCR said in a statement.

Influx

"The situation is so serious that our representative in Chad is now at the border trying to find a solution to this problem, which is leaving the refugees extremely exposed and vulnerable."

Chad threatened on Monday to expel new refugees from Darfur, saying their presence was triggering insecurity, and it called on the international community to take them elsewhere.

Prime Minister Nouradine Delwa Kassire Coumakoye said the influx of refugees into eastern Chad risked becoming a "bone of contention" with Sudan and if the international community did not relocate them, Chad would.

Some reports suggested the armed groups threatening the refugees included Sudanese Toro-boro rebels who back Chadian President Idriss Deby. Chad and Sudan accuse each other of backing rebels to undermine each other's governments.

UNHCR said there were some 8,000 newly-arrived refugees from Darfur in Birak and nearby Korok and roaming armed groups posed a threat to their security, underlining the urgency to deploy a European Union peacekeeping force (EUFOR).

EUFOR has a UN mandate to protect more than half a million Sudanese refugees and displaced Chadian civilians. Chadian rebels have warned EU states not to contribute troops, saying the force will not be neutral because it is dominated by former colonial power France.

UN officials described desperate conditions for the mostly women and children arriving from Darfur. It said some had been raped, while children had become separated from their families.

Many of the new arrivals are exhausted, keen to receive help as soon as they entered Chad even though aid agencies were trying to move them to two camps 50 km from the border.