The army denied on Wednesday there was an army base in Wad Banda and said rebels had attacked the town but that government troops had them surrounded. Ashr said on Thursday the army was nowhere in sight.
The African Union peacekeeping force, struggling to defend itself, has declared the area no-go, making it difficult to verify facts.
PEACE MISSION
The fighting comes just days before Ban starts a multi-state visit to try to set a timetable to revive peace talks between the government and rebels after a May 2006 deal faltered.
It was signed by only one rebel group and neither side has made good on all its commitments under the agreement.
International experts estimate 200,000 people have died since mostly non-Arab rebels took up arms in early 2003 accusing central government of neglecting the region.
Khartoum mobilised mostly Arab militias to quell the revolt, which has created what aid agencies call one of the world's worst humanitarian crises and what Washington calls genocide.
The Sudanese government denies the charge and says 9,000 people have died in Darfur.
A joint U.N.-AU peacekeeping force of up to 26,000 troops and police will take over from the African Union. But the retiring U.N. police chief said on Thursday major Western nations must offer more police for the mission.
"The countries that have been talking about Darfur need to now do something about Darfur with their deployment of police in probably the most desperate place in the world," Mark Kroeker, an American, told reporters in Australia.
The U.N. emergency relief coordinator John Holmes told the BBC that camps in Darfur, housing some 2 million people who fled their homes during the 4-1/2 year conflict, were becoming militarised and politicised.
But he denied the camps had become rebel bases. Last week the Sudanese military attacked Kalma Camp in South Darfur, where it said rebels behind deadly attacks on police were hiding.
