Sudanese rebels and government forces clashed in an oil-producing border state on Monday, Sudan's government and the insurgent group said, a sign of escalating fighting that has raised tensions with the newly-independent south.

Fighting broke out between Sudan's army and rebels in the South Kordofan state in June, just weeks before the south split off into a separate country. Both sides have blamed the other for starting the clashes.

Both Sudan's army and the rebels claimed gains over the other during Monday's fighting in the town of Taludi.

Ahmed Haroun, South Kordofan's governor, said Sudan's military repulsed the attack, and accused South Sudan of backing the rebels.

Hundreds of soldiers from the Sudan People's Liberation Movement (in South Kordofan) were killed during an attack on the city of Taludi this morning, he told reporters at a news conference by telephone.

A spokesman for the SPLA in South Kordofan, Qamar Dalman, said the fighting was not over and disputed the government's figures, saying just five SPLA fighters had been killed.

He claimed rebels controlled up to half of Taludi and had killed 273 government soldiers.

Neither of the reports could be independently verified.

Many of the rebels fought against Khartoum as part of the south's Sudan People's Liberation Army (SPLA) during a decades-long civil war, but were left in the north when South Sudan became independent in July.

South Kordofan and Blue Nile -- both states on Sudan's side of the border -- and the disputed Abyei area saw heavy fighting during the civil war, and fresh clashes have broken out in all three this year.

Sudan has accused groups in those territories of trying to spread chaos along the border, while rights groups have accused Khartoum of trying to stamp out remaining opposition on its side of the border.

FIGHTING EXACERBATES TENSIONS

Fighting along the border has exacerbated tensions between Khartoum and its former civil war foes in South Sudan, who are still negotiating over how to manage the formerly integrated oil industry and other sensitive issues.

Each side has accused the other of backing rebels in its territory.

A spokesman for Sudan's army repeated claims that the South Kordofan rebels received training in South Sudan, an accusation South Sudan has previously denied.

On the other side, South Sudan's army spokesman Philip Aguer said he had evidence linking authorities in Khartoum to the rebel South Sudan Liberation Army (SSLA), which attacked the oil-producing Unity state's Mayom town on Saturday.

Sudan's information ministry official Rabie Abdelaty dismissed the charges. I don't think this accusation has any degree of correctness, he said.

The rebel assault in Unity state killed 11 civilians and 13 government soldiers, Aguer said, adding the South's army killed 32 insurgents and captured three.

The SSLA has advised the United Nations and aid agencies to evacuate both Unity and Warrup state in the next few days, raising fears of further violence.

South Sudan seceded in July after voting to separate in a January referendum promised in a 2005 peace deal that ended what was one of Africa's longest-running civil wars.

(Reporting by Khaled Abdelaziz; Writing by Alexander Dziadosz; Editing by Matthew Jones)