Sudanese warplanes have launched air strikes against a key rebel-held town in war-torn South Kordofan state, the insurgents said on Sunday, but there were no reports of casualties.

"Two Sukhoi jet fighters attacked Kauda town," the Sudan People's Liberation Movement-North said in a statement.

The military's spokesman could not be immediately reached.

SPLM-N has previously reported bombings of Kauda, including in December 2012.

Nuba Reports, a website based in South Kordofan, said one of its "citizen reporters" witnessed Saturday's attack on the town about 100 kilometres (60 miles) east of the state capital Kadugli.

It said residents took cover in foxholes as a pair of Sukhoi jets made two passes over the town, firing multiple "rockets" that struck educational facilities, a football pitch near the market, and killed some sheep.

International rights groups have accused the Sudanese military of "indiscriminate" aerial attacks during the war which began nearly three years ago.

Khartoum has said that rebel shelling of Kadugli since late 2012 has killed civilians.

The revolt by the non-Arab SPLM-N is fuelled by complaints of political and economic neglect by the Arab-dominated Khartoum regime.

Defence Minister Abdelrahim Mohammed Hussein said in November that the army had launched an operation to crush rebels in Kordofan and elsewhere.

More than one million people have been severely affected or displaced by the fighting in South Kordofan and in Blue Nile state, where SPLM-N is also in revolt, the United Nations says.