"A train transporting southern returnees from Kosti to Wau was attacked by a Misseriya militia this morning in the area of Meiram, around 50 kilometres (30 miles) south of Muglad," Hua Jiang, a spokeswoman for the UN peacekeeping mission in Sudan, said.
One person was killed and four wounded in the raid, Jiang said.
Meiram lies in north Sudan's embattled state of South Kordofan, just next to Darfur and the tense Abyei border region, while Muglad is the historical capital of the Misseriya tribe.
The heavily armed Arab nomads were a key proxy militia of Khartoum's army during its 1983-2005 conflict with the former southern rebel army, the SPLA.
One of the tribe's chiefs, Omar al-Ansari, confirmed the train attack had happened in a Misseriya area, but denied that his people were responsible.
"The train faced technical problems in a place called Hierika, close to South Darfur, and that was when a group of Darfur rebels attacked it and grabbed some belongings from the passengers," Ansari told AFP by phone.
He said no one was killed.
Tensions are running high between north and south Sudan in the run-up to the south's formal declaration of independence on July 9, driven by conflict in the border areas of Abyei and South Kordofan, and exacerbated by the lack of progress in negotiating key unresolved issues.
Northern troops overran Abyei last month in response to a deadly attack on an army convoy, prompting more than 100,000 residents to flee south, and with the Misseriya reportedly moving in with Sudanese soldiers to fill the vacuum.
Around two weeks later, on June 5, another conflict erupted between the northern army and fighters aligned to the south, in neighbouring South Kordofan, where the United Nations said on Sunday that civilians were among the victims of the latest air strikes on rebel positions.
Khartoum: Misseriya Arab militiamen on Sunday carried out a deadly attack on a train carrying south Sudanese home, just two weeks before their region celebrates full independence from the north, the UN said.
First Published: Sunday, June 26, 2011, 23:56