The mission, led by Bacre Waly Ndiaye, Director of the UN Human Rights Office in New York, has started in neighbouring Chad, where tens of thousands of Sudanese have fled over the past year to escape the violence.

The team will interview Sudanese refugees taking shelter there before travelling to Darfur itself to assess the situation. The mission is expected to last about 10 days, a UN spokesman told reporters today in New York.

Bertrand Ramcharan, the Acting High Commissioner for Human Rights, set up the mission to investigate reports that systematic human rights abuses are occurring against civilians in Darfur.

Last Friday Jan Egeland, the Under-Secretary-General for Humanitarian Affairs and Emergency Relief Coordinator, said a coordinated, "scorched earth" campaign of ethnic cleansing was taking place in Darfur, which is in Sudan's west.

Mr. Egeland said the region's black African population, especially the Fur, Zaghawas and Massalit ethnic communities, were being forcibly driven away from the area by militia groups allied to the Sudanese Government.

Militia groups, the Sudanese Government and rebel groups have been fighting in Darfur for just over a year.

As the fact-finding mission begins work, the UN Office in Sudan is reporting that conditions in Darfur have worsened in some areas, a UN spokesman said.

He said outbreaks of communicable diseases, such as measles, are increasing because of the rising number of internally displaced people moving to relatively urban areas in Darfur. Some 200 cases of measles have been confirmed in one camp alone.

Humanitarian agencies say they cannot provide enough food, clean water, shelter and health care to internally displaced Sudanese because of the lack of security in Darfur.