Some of the newly displaced have fled to camps like this one, Zam Zam, which holds more than 100,000 people, outside the town of El Fashir in North Darfur. Over the years, the camp has become such a fixture of the conflict in Darfur that many of its residents have lived here long enough to build permanent cottages of mud and straw.

War in Darfur broke out a decade ago when non-Arab rebels took up arms against the central government in Khartoum, accusing it of neglect and discrimination. The government responded with overwhelming force, using militias that came to be known as the janjaweed.

Only last year, there were some hopeful signs of improvement, with the United Nations reporting that tens of thousands of Darfurians had voluntarily left camps and returned home to rebuild their lives. They represented only a tiny fraction of the hundreds of thousands displaced by years of fighting, but to many officials, the exodus from the camps seemed an indication that the situation could be improving.

But in other parts of Darfur, conflict still raged, undercutting the early signs of progress. Now, the surge of new displacements is worrying officials from the United Nations and the African Union, who say that thousands of civilians fled the towns of Labado and Muhajeria in April when fighting broke out between Sudanese forces and one of three main Darfurian rebel groups that continue to fight the government.

Beyond that, fighting among Arab groups over the ownership of gold mines in the Jebel Amer area this year also displaced thousands.