A senior United Nations humanitarian official says the world body is "extremely worried" about the situation in Sudan's South Kordofan region after a leaked report said war crimes may have been committed there.
The leaked UN report, which emerged on Monday, documents witness accounts of suspected atrocities and called for an inquiry into the allegations.
"I think we are all extremely worried about the situation there and the alarming allegations we are hearing of mass graves, disappearances of civilians, targeting of people on an ethnic basis," Valerie Amos, the UN's undersecretary for humanitarian affairs, told Al Jazeera.
"It's very important that these allegations are investigated," she said.
Oil-rich South Kordofan borders the newly created nation of South Sudan. It has seen intense fighting in recent months between the Sudan's army and local armed groups.
Both sides are accused of targeting civilians, according to the leaked UN report, but it says the government in Khartoum is responsible for some of the worst abuses.
Daffa-Alla Elhaj Ali Osman, the Sudanese ambassador to the UN, told Al Jazeera that only anti-government fighters were to blame for the violence.
"I can assure you that there was not a single civilian casualty during those operations which targeted SPLM forces, and there were no casualty reports," he said.
Difficult to investigate
The UN's mandate to be in Sudan expired on July 9, and the government refuses to grant an extension, making it difficult to conduct investigations into the reports of the violence there.
"The Security Council would very much like to know what is happening in South Kordofan and would like us to be able to get in and get help for the people who need it," Amos said.
"It is very hard when you have a sovereign government that is refusing to allow anyone in to investigate what is happening, is refusing to let us have humanitarian workers who operate independently without bias to actually go in and see what is happening, and see whether or not there are people who need our assistance."
The UN had received reports of more than 73,000 people being displaced, Amos said.
Another 7,000 people who were seeking health and shelter in front of a UN compound in South Kordofan disappeared, she added. "We don't know where they have gone."
Amos said it was difficult for a body like the UN to act in a situation where they were unable to use international pressure to persuade the different factions to negotiate.
"If you have a government that is refusing to listen and opposition and other armed groups that are not listening either, the ability to make a difference is severly hindered," she told Al Jazeera.
Amos added that there had been some negotiations with the Sudanese government, as well as an agreement that was negotiated through the African Union.
Meanwhile, some 4,000 Ethiopian peacekeepers have gained approval to enter South Kordofan, and Amos said the UN was hoping to see them there as quickly as possible.
"But we were not able to get a ceasefire brokered as part of that deal," Amos said.
For six weeks, heavy fighting has raged across the area, between the army and Nuba armed groups who fought with the SPLA - the ex-rebel army of the south - during their decades-long conflict with Khartoum.
South Sudan proclaimed formal independence from the north on July 9, and observers say opposition from north Sudan's neglected peripheral regions such as Darfur and South Kordofan may grow in the wake of southern secession.