Sudanese government troops have clashed with Darfur rebels in southern Darfur.
The fighting comes after a wave of government bombings against rebel positions in South Darfur.
It is not clear if there were any causalities.
Last week, rebels from the Justice and Equality Movement seized control of a strategic town in South Darfur, Muhajiriya, from a rival rebel group, the Sudan Liberation Movement of rebel leader Minni Minawi.
Sudanese government warplanes bombed rebel targets during the fighting.
The governor of South Darfur, Ali Mahmoud, told the Sudan Media Center that army troops are preparing to reclaim the city from the JEM rebels.
Muhajiriya was seen as a stronghold for Minawi, the only Darfur rebel leader who has signed a peace deal with the Sudanese government.
The joint African Union - United Nations peacekeeping mission in Darfur says it has grave concern for the lives and safety of Muhajiriya's 30-thousand residents, some of whom are displaced civilians.
Darfur rebel groups launched an uprising against the Khartoum government in 2003. U.N. experts say the fighting has killed more than 200,000 people and displaced more than 2 1/2 million others. Sudan puts the death toll much lower, at 10,000.