The United Nations refugee agency says at least 12,000 people from Sudan's Darfur region have fled to neighboring Chad after Sudanese air strikes in West Darfur.
Spokeswoman for the U.N. High Commissioner for Refugees Helene Caux said Sunday the refugees crossed the border after the Sudanese army attacked three towns Friday and Saturday. The agency says it is sending a team to investigate the situation.
Sudan's army has confirmed the military operations in the towns of Abu Suruj, Sirba and Suleia. The army says it was trying to clear rebels out of the area.
The U.N. has said it has preliminary reports confirming an estimated 200 casualties from the attacks.
U.N. Secretary General Ban Ki-moon has strongly condemned the assaults and demanded that all parties in Darfur refrain from attacking civilians.
In other developments Saturday, Sudan signed an agreement with the joint United Nations-African Union mission in Darfur to give the troops a legal framework for their operations.
The mission's 26,000 troops and police will eventually replace an A.U. force of seven-thousand peacekeepers.
Five years of fighting in Darfur has killed about 200,000 people and displaced more than 2.5 million others.
The violence broke out in early 2003 when rebels took up arms against the Sudanese government. Sudan's Arab-dominated government has been accused of backing militias that commit atrocities against Darfur's ethnic African communities in the fight against the rebels.
Some information for this report provided by AP and Reuters.