The United Nations Mission in Sudan says fighting in a state along Sudan's north-south border has intensified and spread.

Spokeswoman Hua Jiang said Wednesday the mission has received reports of more deaths in the capital of South Kordofan state, Kadugli. She added that U.N. patrols have not been able to verify the claims because of the heavy fighting.

The U.N. spokeswoman also said the clashes between the north's Sudanese Armed Forces and elements of the south's Sudanese People's Liberation Army have spread to hills surrounding Kadugli.

Jiang told VOA that about 7,000 people in Kadugli have fled to a security zone adjacent to a U.N. peacekeepers' compound. She said the U.N. mission is working with other agencies to provide those people with humanitarian aid.

Escalating clashes in South Kordofan and the disputed Abyei region have raised concerns Sudan may be on the brink of a new north-south civil war.

The south is preparing to declare independence from the north on July 9, but the sides remain split on several key issues, most notably the future of oil-rich Abyei.

North Sudanese forces seized control of Abyei last month and Khartoum has rejected international calls to withdraw its troops.

The United Nations Security Council has described Sudan's military operations in Abyei as a “serious violation” of the 2005 Comprehensive Peace Agreement. That agreement ended the 21-year north-south war.

South Sudan voted to split from the north in a January referendum. Abyei was scheduled to decide at the same time on whether to join the north or the south, but that referendum failed to happen because the sides could not agree on who was eligible to vote.