Heavy fighting in Sudan's Blue Nile state has killed 13 soldiers and one rebel.
In a statement, rebels said their ambush and subsequent six-hour battle last Tuesday, 20km south of the state capital Damazin, also injured 17 government troops and three insurgents from the Sudan People's Liberation Movement-North (SPLM-N).
The reported fighting came on the same day that Sudanese and South Sudanese forces resumed clashes along their border, bringing them close to a return to outright war.
South Sudan separated last July in an overwhelming "yes" vote after decades of war.
The South denies Khartoum's claim that it supports the SPLM-N, ethnic rebels who have been battling the government since last year in Blue Nile and South Korfodan states.
Sudan's army spokesman, Sawarmi Khaled Saad, said rebel scout teams have clashed with government troops in Blue Nile but were defeated.
Khartoum has cited security concerns in placing tight restrictions on the operations of foreign relief agencies in both South Kordofan and Blue Nile states.
The United Nations says the fighting has displaced or severely affected 350,000 people.
United States officials have warned that about 250,000 people could soon go hungry in the region.
