By Alex Dziadosz
KHARTOUM (Reuters) - Huts were still burning and looters roamed the main town of Sudan's disputed Abyei region this week, a senior U.N. official said, more than a month after Khartoum seized it and shut down a joint north-south administration.
Kyung-wha Kang, U.N. Deputy High Commissioner for Human Rights, said "thorough" investigations were needed in Abyei and another conflict-stricken border region, where weeks of fighting has forced tens of thousands of people to flee.
South Sudan will become a separate country in a little over two weeks, but clashes along the ill-defined border have raised fears of a return to the all-out north-south civil war that killed more than two million people over decades until 2005.
Fighting erupted between the northern army and southern-aligned fighters in the oil state of Southern Kordofan on June 5, about two weeks after Khartoum seized the neighboring contested Abyei region with tanks and soldiers.
Kang said a drive through Abyei's main town this week showed "complete destruction. No civilians. Some huts still burning, smoke, looters still roaming around".
"I think the situation is serious enough that it requires a thorough investigation," she said in an interview late on Tuesday.
The northern army, which says its troops are in Abyei and Southern Kordofan to guarantee stability and protect civilians, has called for Abyei's residents to return home.
Kang said human rights monitors should be given more access to the area to conduct interviews with people involved in and affected by the fighting on both sides.
"We would like that opportunity, but so far access has been very limited," she said.
Thousands of residents who had fled Southern Kordofan's state capital of Kadugli and the surrounding area to shelter near a U.N. mission in Sudan compound had returned home, but it was questionable whether the return was voluntary, Kang said.
She said her team had asked to visit Southern Kordofan during a tour of Sudan ahead of southern secession on July 9, but they had not heard back yet.
"Kadugli also requires a thorough, thorough look," Kang said. "The sooner the better".
Separate human rights and church groups have accused Khartoum of waging a campaign targeting the ethnic Nuba population in Southern Kordofan -- a northern state -- because of their perceived support for the south.
Northern officials have dismissed such charges as politically motivated allegations without grounds.
Air space has been largely restricted for U.N. flights over Southern Kordofan, which the world body has said has endangered its aid work in the area.
The United Nations also said six of its national staff were arrested at Kadugli airport on Wednesday.
Sudan has a long history of violent conflict.
The January referendum in which southerners voted to secede was a condition of a 2005 deal to end a civil war fought over ideology, ethnicity, religion and oil which forced millions to flee their homes.
Kang said the new nation in the south would face "enormous" human rights challenges, exacerbated because infrastructure and state capacity were still lacking.
"War leaves behind a culture where brute force gets its way," she said. "Overcoming that culture will require a lot of time, a lot of support, a lot of push".
(Editing by Philippa Fletcher)