|South Kordofan has witnessed violence in the state since June, prior to the creation of South Sudan [Reuters]
Clashes between troops and anti-government fighters in the Sudanese state of South Kordofan have killed dozens of people, UN and opposition sources say, with a non-governmental organisation worker reportedly among the dead.
Fighters from the Sudan People's Liberation Movement-North, or SPLM- North, attacked a checkpoint on Thursday in the Kurgul area, around 35km south of Deleng, reportedly killing 12 Sudanese soldiers at around 05:30 GMT, a UN source said, requesting anonymity.
Three vehicles were caught in the crossfire, including two private buses and a car belonging to an international NGO, in which a Sudanese staff member was killed and his driver seriously wounded, the source added.
The road, the main land route to South Kordofan state's capital, Kadugli, runs through a mountainous area known to host SPLM-North fighters.
Clashes between the Sudanese army and SPLM/A fighters in South Kordofan broke out in June, just one month before the independence of South Sudan.
Separate battles on Thursday indicate that four months later the conflict, which was apparently triggered by the army's insistence on disarming SPLA elements, is still intense.
The SPLM/A fought with the former anti-government army of the south during their decades-long war with Khartoum.
Heavy fighting reported
Earlier, the fighters and the army reported heavy fighting in the state's eastern Rashad district, with both claiming to have killed dozens on the opposing side.
A spokesman for the SPLM-North said they had killed around 60 soldiers in the early-morning attack on an army position.
"The SPLA launched a heavy attack in the Rashad area early this morning," Arnu Ngutulu Lodi, a spokesman for the fighters, told the AFP news agency.
"They killed 60 SAF (Sudan Armed Forces) troops and destroyed 13 mounted land cruisers."
A number of fighters had also been killed, he said, without elaborating.
The commissioner of Rashad district, Khaled Mukhtar, quoted by the semi-official Sudan Media Centre website, confirmed that the SPLA had launched a surprise attack on the army, near the border with South Sudan.
But he said the fighters had suffered heavy losses.
"More than 30 of them were killed, among them an officer, and two fighters were taken prisoner" and the army had also captured a large amount of weapons, Mukhtar said.
It has been very difficult to get independent information on the border conflict, with the UN peacekeeping mission disbanded in July and most international NGOs denied access to the region.
Another SPLM source said on Thursday that the Sudanese air force had bombed a village near the town of Talodi, where clashes were reported earlier this week, and that a local leader had been killed.
"The village does not have any military presence, and the raid seems to have been carried out because the villagers refused to join the Popular Defence Force," Gamar Delman said, referring to the feared group that is now part of the Sudanese army.
Khartoum has sought to reassert its authority within its new borders since South Sudan's recognition as the world's newest nation on July 9, moving to disarm troops outside its control.
South Kordofan and Blue Nile, where a similar conflict broke out on September 2, are located just north of Sudan's new international border.
But they both have large numbers of SPLM-North supporters and troops, who have historic political ties to Khartoum's former civil war enemies, now the ruling party in Juba.
Earlier this week, the UN human rights envoy for Sudan warned that the ongoing violence in the border region could jeopardise peace between north and south.
"Sudan and South Sudan cannot be at peace if the border areas between the two countries remain mired in armed conflict," Mohamed Chande Othman told the UN Human Rights Council.