KHARTOUM - Sudan said on Wednesday it would use "all legitimate ways and means" to oppose what it said was South Sudan's assault on an oil-producing border region disputed between the two countries and long marred by clashes.

The two former civil war foes have accused each other of provoking the clashes in the disputed area around Sudan's South Kordofan border state. South Sudan, which declared independence in July, has been locked in a dispute with Khartoum over oil payments and other issues.

Sudanese rebels said the South's government was carrying out air and ground attacks in South Kordofan on Wednesday. Sudan's military spokesman could not immediately be reached for comment.

South Sudan's army (SPLA) said it had repulsed an attack on Tuesday and pursued Sudanese troops into the disputed Heglig area, vital to Sudan's economy because it has an oil field that accounts for about half of its 115,000 barrel-a-day output.

But Khartoum said it was an aggression.

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