Sudanese troops have denied UN and African Union peacekeepers access to a town in the country’s western Darfur region to investigate reports of an alleged mass rape of about 200 women and girls, the UN said on Wednesday.

The joint peacekeeping mission, Unamid, is deeply concerned about reports of attacks in Tabit, UN spokesman Stephane Dujarric told reporters in New York. “A verification patrol was denied access to Tabit, in North Darfur, by Sudanese military at a checkpoint,” Dujarric said.

A peacekeeping team travelled to the Zamzam camp for displaced people on Wednesday to assess whether anyone had arrived from Tabit. “The team concluded that no recent displacement from Tabit had occurred,” Dujarric said, and added that no complaints about the incident had been received by the chief prosecutor of North Dafur.

Law and order have collapsed in much of Darfur, where rebels took up arms in 2003 against the Arab-led government in Khartoum, which they accused of discriminating against them. Unamid, has been deployed in the region since 2007.The conflict has killed as many as 300,000 people and displaced 2 million, according to the UN.