Sudan says its forces have clashed with Chadian army deserters in the western region of Darfur.
By Jonah Fisher
BBC News, Khartoum
A statement issued in the capital Khartoum said military operations were underway to expel the men. However it made no mention of casualties.
The Chadians mutinied from their army in September this year and claim to number in the hundreds. They say they want to overthrow their president.
According to Sudan, the Chadians number about 120.
For three days the Sudanese army has attacked positions in the mountains of Darfur, the deserters being their declared target.
The men mutinied in September and fled to Darfur, pledging to overthrow Chad's President Idriss Deby.
They have spent the last month roaming western Darfur and according to Khartoum, looting and killing civilians.
There has been no official word on the number of casualties in the fighting, but one of Darfur's smaller rebel groups said the government had attacked and burned three villages with at least nine civilians killed.
The long border between Sudan and its western neighbour is porous, with a murky mix of rebel groups and armed militia roaming its arid landscape.
A ceasefire is supposed to be in place but both the Sudanese army and the rebel movements have broken it with regularity.