Fighting has erupted in a disputed border region between Sudan and South Sudan, with the Sudanese army claiming a strategic victory in its offensive against rebels in the state of South Kordofan.

The army said on Saturday it had captured camps on a key supply route after deadly clashes.

"Today the Sudanese army took control of SPLA-N (Sudan People's Liberation Movement - North) camps in the lake Jau area," said Sawarmi Khaled, an army spokesman.

"The fighting took place at around 4:30pm (13:30 GMT). There were a number of casualties and injured soldiers on both sides.

"This is a strategic area because it is a gateway to the south. The SPLA-N receive their weapons and ammunition and supplies through it."

South Kordofan and Blue Nile states served as the ninth and tenth divisions of the southern rebel forces during the decades-long civil war between south and north, but the peace pact that ended the conflict placed the areas they fought for in the north.

Many SPLA-N fighters' uniforms still show the flag of the former rebel group that now governs South Sudan, which voted in a referendum for secession.

Sudan accuses its southern neighbour of arming fighters in the two states and has taken the matter to the UN Security Council, but South Sudan rejects the charges.

Fighting in South Kordofan first erupted in early June, just weeks before the independence of South Sudan, between the Sudanese military and Nuba armed groups who fought alongside the former southern rebels.

Saturday's fighting came weeks after rebels in Sudan's Darfur region and in the states of South Kordofan and Blue Nile announced the formation of an alliance to overthrow the government of Omar al-Bashir, Sudan's president.

The rebels said the alliance, called the Sudanese Revolutionary Front, was bent on "toppling the regime of the [Sudan's ruling] National Congress Party with all possible means" and replacing it with a democratic system.

'Heavy bombardment'

The SPLA-N rebels were not immediately available to comment on the army's claimed victory on Saturday. But it follows days of heavy fighting just north of Jau, a lakeside town on a disputed stretch of the north-south border.

Yasser Arman, the SPLM-N leader, has said that Khartoum had launched a major military campaign in South Kordofan earlier this week.

"There is a heavy bombardment against civilian populations and massive displacement," Arman said in a statement.

"This offensive is going to result in a much bigger humanitarian crisis than the last offensive that started in June."

Sudanese troops attacked SPLA-N positions on Wednesday in Buram county with heavy artillery and tanks, according to other rebel sources.

A barrage of army air strikes reportedly killed two civilians and badly injured four others in the area.

The Sudanese government has prevented foreign aid workers and journalists from visiting the region, making it hard to verify information about the ongoing violence in Sudan's two embattled border states.

In addition to the fighting in South Kordofan, there has been evidence of cross-border attacks in recent weeks, the AFP news agency reported.

Witnesses said the army bombed a refugee camp last month in South Sudan's neighbouring Unity state, just south of lake Jau, badly fraying relations between the former civil war enemies.

The UN refugee agency said last week that the number of people fleeing the unrest in Blue Nile and South Kordofan was likely to reach 100,000 by the end of the year, up from about 80,000 now.