Mortar rounds landed near UNICEF offices in Kadugli, the capital of South Kordofan, this week. The United Nations said that it relocated its staff to the nearby offices of the U.N. Interim Security Force in Abyei as a precautionary measure.
South Sudan gained independence last year as part of a 2005 peace deal that ended the Sudanese civil war. Ethnic fighting, disputes over oil revenue and border conflicts have threatened the peace deal, however.
Abyei is a disputed border area near the southern border of South Kordofan.
Jens Laerke, a spokesman for the U.N. Office for the Coordination of Humanitarian Affairs, said relief efforts were complicated because of the presence of the rebel Sudan People's Liberation Movement-North.
"U.N. and humanitarian partners have not been able to deliver assistance to people in need in the SPLM-North controlled areas of South Kordofan for quite some time but are continuing to provide relief assistance to people affected by the fighting in government-controlled areas of the state," he said in a statement.
No group has claimed responsibility for the attacks in South Kordofan. At least six people were killed in the attacks.