KHARTOUM More than 15,000 people have fled Sudan's Abyei region to the south after the northern army seized the disputed area and parts of the main town were burned and looted, United Nations officials said Tuesday.
A senior southern minister in the Khartoum government resigned, protesting against what he called war crimes committed by the northern army which had moved tanks into the main regional town over the weekend after weeks of tensions.
Analysts fear north-south fighting over Abyei could reignite a full-blown conflict in Africa's largest country, a move that could have a devastating impact on the surrounding region.
Southerners voted in January for independence in a referendum agreed under a 2005 peace deal but Abyei remains the most contentious point in the build-up to secession on July 9.
Khartoum has defied calls by the U.N. Security Council and world powers to withdraw its forces from Abyei, which has oil and fertile grazing land.
U.N. officials said between 15,000 and 20,000 people fled Abyei and arrived in or around Agok, a town just across the southern border.
"The situation is very volatile and fluid," said Elizabeth Byrs of the United Nations Office for the Coordination of Humanitarian Affairs.
The U.N. said a team of its experts and aid groups visited Agok Monday to assess the situation and estimate the number of refugees there, but gunfire erupted in the town while they were meeting local officials and the mission was cut short.
Armed looters burned parts of Abyei town Monday, the U.N. said.
Sudan's cabinet affairs minister, Luka Biong, a key southerner in the government of President Omar Hassan al-Bashir, resigned in protest against the events in Abyei.
"These are real war crimes. I have never seen such suffering. Houses are burned in Abyei town and south of it," Biong told Reuters.
He said the ruling northern National Congress Party (NCP) had no interest in finding a peaceful solution on Abyei and other issues with the south on the negotiating table.
North Sudan says it sent in troops to clear out southern soldiers who it said had broken agreements by entering the area.
France, which currently holds the presidency of the United Nations Security Council, called on the northern army to withdraw immediately from the positions taken.
"In addition France calls for the Sudanese government to protect the civilian population against attacks and unacceptable looting that has happened in Abyei since Sunday," Foreign Ministry spokesman Bernard Valero told reporters.
Abyei remains the most contentious point in the build-up to the secession of the south, where 75 percent of the country's 500,000 barrels a day oil production comes from.
Southerners overwhelmingly voted for independence in the January referendum. The 2005 peace deal also promised Abyei residents their own referendum over whether to join the north or south, but that never took place as neither side could agree who was qualified to vote.
(Additional reporting by Khaled Abdelaziz in Khartoum, Barbara Lewis in Geneva and John Irish in Paris, Editing by Maria Golovnina)