The violence in West Darfur broke out after a dispute between Arab and African ethnic groups in the state capital of el Geneina.
Violence in Sudan's West Darfur region over the past week has left at least 65 people dead and more than 50 injured, as well as displacing thousands, an international peacekeeping mission said on Friday.
The intercommunal clashes that erupted on Dec. 29 were the worst in West Darfur for years, though details of casualties have been slow to emerge.
The violence presents a challenge to military and civilian authorities sharing power following the overthrow of former president Omar al Bashir last April. They are trying to broker lasting peace in Darfur and other parts of the country affected by civil conflict.
The violence in West Darfur broke out after a dispute between Arab and African ethnic groups in the state capital of el Geneina. Arab militiamen raided a camp for internally displaced people and attacked and burned several villages, according to residents.
The joint African Union-United Nations peacekeeping mission in Darfur, UNAMID, said on Friday it was deeply concerned by the "deterioration of the security and humanitarian situation in el-Geneina and the surrounding area".
Conflict spread in Darfur in 2003 after mostly non-Arab rebels rose up against Khartoum. Government forces and mainly Arab militia which moved to repress the revolt were accused of widespread atrocities.
West Darfur had been largely calm since 2010, though there were occasional skirmishes over the past three years.
On Thursday and Friday there were also clashes in the east of the country at Port Sudan between Beni Amer and Nuba ethnic groups that left eight people dead and dozens injured, according to a local doctors' group.
The Beni Amer and Nuba have clashed in the past but signed a reconciliation deal last September following violence that left at least 16 dead.