A rebel spokesman says that Sudan's military is carrying out a bombing campaign intended to shut down the main route for refugees fleeing violence in the country's south.

Arnu Loddi, a spokesman for the Sudan People's Liberation Movement-North, a rebel group inside Sudan, said Monday that attacks by the Sudanese Armed Forces have been focused along the road leading out of Southern Kordofan, Sudan, into Yida, South Sudan.

A Sudanese military spokesman did not immediately answer calls seeking comment about the reports.

More than 20,000 refugees already have fled to a camp in Yida to escape the violence, and the United Nations worries that hundreds of thousands more could be on the way.