Sudanese military planes dropped bombs on border villages in the western part of the country Monday, sending hundreds more civilians into neighboring Chad.
Witnesses say loud explosions were heard in the desert frontier that separates Sudan and Chad, and report seeing bombs hitting civilian homes.
It is not known if the attacks have resulted in civilian casualties.
The United Nations refugee agency estimates some 95,000 civilians have fled to Chad since the conflict between two western-based rebel groups and the Sudanese government erupted last year.
Aid workers say they are concerned about the refugees, who travel for days in harsh terrain and extreme weather conditions. Earlier this month, the U.N. World Food Program issued an appeal for $11 million to help feed thousands of Sudanese refugees now living in camps just across the Chadian border.
The conflict in Sudan's western Darfur region has escalated at the same time the government has made significant progress towards a comprehensive peace settlement with southern-based rebels. A deal would bring an end to 20 years of civil war.
On Saturday, The New York Times reported the U.N. refugee agency is investigating reports that as many as 18,000 more Sudanese refugees crossed into Chad just last week alone.
Some information for this report provided by Reuters and AP.