Heavy bombardments and armed attacks by Sudanese forces and Janjawid militias took place in three towns in western Darfur on Friday and Saturday.Hundreds of casualties
The new joint African Union-United Nations peacekeeping force received preliminary reports of about 200 casualties but it is not known if this included the number of injured.
On Saturday the Sudanese army confirmed that its troops had carried out military operations.
"Army forces carried out large-scale operations combing the areas of Abu Suruj, Serba and Salia," Othman Mohammed al-Agbash, an army spokesman, said.
Ban Ki-Moon, the UN secretary general, on Saturday condemned the attacks and demanded that all parties adhere to international humanitarian law, which prohibits military attacks on civilians.
On Sunday, the Justice and Equality movement (JEM) warned that the joint UN and African Union force against moving into the towns, delaying any investigation.
"We are warning the hybrid troops forces that they should not enter these areas. We are coming back," Khalil Ibrahim, the leader of the Darfuri rebel group, said.
"We will not accept them coming. We will attack anybody who comes into our areas."
The latest unrest comes after a senior UN official on Friday warned that a proxy war between Sudan and Chad through rebel groups threatened to further destabilise the region.
International experts estimate that 200,000 people have been killed and 2.5 million more have been displaced in five years of conflict in Darfur.