Khartoum – Fighting erupted on Sunday in South Kordofan, Sudan's volatile oil-producing border state, a UN spokeswoman said, where the north is pressuring the Sudan People's Liberation Army to disarm.
The former southern rebels said the fighting began when a group within the northern army refused to disarm the SPLA troops, a claim the army denied.
The United Nations mission in Sudan confirmed the clashes but was unable to say who the fighting was between.
"There were two attacks. One happened in Kadugli town itself, where a police station was attacked last night (Saturday) by unknown gunmen," UNMIS spokeswoman Hua Jiang told AFP, adding that there was no information on casualties.
"We have also had reports of shooting in Um Dorain today. We have sent land and air patrols to the area to investigate," she said.
Tensions are running high in the heavily armed state, a former civil war battleground with strong links to the south which is due to split with the north in one month.
The army acknowledged that there had been fighting in Um Dorain, a former SPLA stronghold around 35km (22 miles) southeast of Kadugli, but insisted it was an "isolated incident."
"A soldier fired indiscriminately, for personal reasons, and the situation is now under control," the northern Sudanese Armed Forces spokesman, Sawarmi Khaled Saad, said in a statement published by the official SUNA news agency.
However, the SPLM, the state's political branch of the SPLA, said the clashes took place because of a rebellion against northern police by a group of SAF troops in the 14th infantry division who refused an order to disarm the SPLA.
The SPLM said in a statement obtained by AFP that the fighting started late on Saturday in Kadugli, the state capital, and then spread to Um Dorain.
It also accused officials at the highest levels of government of calling for war in South Kordofan and Blue Nile and of sending military hardware and troops from Khartoum.
The army has ordered northern SPLA troops in the two border states, thought to number around 40,000, to redeploy south of the 1956 borders before southern independence or face unspecified consequences.
Though not new, the threats have become more vocal since Khartoum's troops overran the contested Abyei region nearby, on 21 May, and razed much of the main town, prompting at least 60,000 people to flee, according to UN estimates.
Analysts have warned of the Khartoum government asserting itself aggressively ahead of southern independence, partly in an effort to establish itself as the dominant partner in their future relationship.
The SPLM said on Sunday that its men were entitled to remain in South Kordofan until April 2012 as members of the special Joint Integrated Units of northern and southern personnel, both army and police, under the 2005 peace agreement.
There have been major security concerns in the troubled border state for some time, compounded last month by disputed gubernatorial elections and by the SAF's occupation of nearby Abyei.
Former deputy governor Abdelaziz al-Hilu pulled out of the race shortly before the results of the election were announced, alleging fraud and leaving the ruling National Congress Party's candidate, incumbent governor Ahmed Harun, unopposed.
Hilu is number two in the northern branch of the SPLM, and was competing against NCP stalwart Harun, who is wanted by the International Criminal Court on charges of war crimes committed in Sudan's western Darfur region.
Hilu had blamed his rival for organising an attack by northern militiamen on his village in the eastern part of the state, in April, in which 29 people were killed, including women and children.
