An attack by rebels in the capital of South Kordofan state in Sudan killed five and wounded 23 on Monday, according to the BBC.
A United Nations worker said five shells landed around Kadugli. The BBC said rebels have been fighting in South Kordofan near Sudan's southern border since last year, but the state capital was largely peaceful until now.
A spokesman for the Sudanese army said, "This morning a group from SPLM-North tried to get inside Kadugli town and they shelled an area six kilometers (four miles) east of Kadugli. As a result of this a woman was killed and three citizens injured," according to Agence France Presse, giving a lower death toll than the government radio station.
AFP said a spokesman for the SPLM-N rebel group acknowledged that they were behind the attacks.
South Sudan denies backing the rebels.
More on GlobalPost: Sudans strike deal on border security, oil
The UN said its staff was moved to a peacekeeping base "as a precautionary measure," the BBC said.
Just last month, Sudan and South Sudan signed security and cooperation deals in hopes of ending the conflict between their countries.
Meanwhile, a Sudanese military plane carrying personnel and equipment to Darfur crashed near Khartoum, killing 15 people. The crash happened on Sunday, when the plane's engine stopped working, Reuters reported.
The pilot was attempting an emergency landing when it crashed, killing 13 people instantly and injuring nine. Two of those injured later died from their wounds, state news agency SUNA reported.
Reuters noted that there have been several crashes in Sudan in recent years, as US sanctions have made it difficult to obtain spare parts for airlines.
More on GlobalPost: At least 19 soldiers killed in truck accident in Egypt's Sinai