KHARTOUM (Reuters) - Sudan's northern army seized control of the disputed, oil-producing Abyei region, officials said on Sunday, forcing thousands to flee and bringing the country's north and south to the brink of full conflict.
Khartoum sent tanks into Abyei town, the area's main settlement, on Saturday, the United Nations said after weeks of growing tension and accusations of skirmishes by both sides.
Analysts fear northern and southern fighting over Abyei could reignite a full blown war in Sudan, a development that could have a devastating impact on its neighbours which include Kenya, Uganda and Ethiopia.
Control over Abyei remains the biggest point of contention in the countdown to the secession of south Sudan, expected in July.
The escalation of violence in the fertile border region was condemned by the United States, Britain and U.N. Security Council envoys who were visiting Sudan.
"The members of the Security Council call upon the government of Sudan to halt its military operation and withdraw immediately from Abyei town and its environs," French U.N. Ambassador Gerard Araud told reporters in Khartoum, reading from a council statement.
The council also condemned an attack by south Sudanese forces on a U.N. convoy in the region on Thursday.
U.N. officials said the north had sent at least 15 tanks into Abyei town.
"Most residents in Abyei town left yesterday (Saturday) and have gone south. There are reports of looting by armed groups," U.N. spokeswoman Hua Jiang told Reuters, adding the town's population was estimated at around 20,000.
Southerners overwhelmingly voted to declare independence from the north in a January referendum, promised in the 2005 peace deal that ended the last north-south civil war.
That conflict between the mainly Muslim north and the south, where most people follow Christian and traditional beliefs, killed an estimated 2 million people.
Analysts said there was a risk that a new north-south war could have an equally serious impact and fighting could spread over Sudan's borders disrupting some of east Africa's most promising economies.
In the previous war, countries bordering Sudan were flooded with refugees during the fighting. Khartoum was also accused of arming militias, including Uganda's rebel Lord's Resistance Army, to destabilise the south. The north denied the allegations.
North Sudan said it had sent its troops to Abyei to clear out southern soldiers that it said had entered the area, breaking the terms of earlier agreements.
"The Sudanese armed forces control Abyei and are cleansing it of illegal forces," Amin Hassan Omar, a minister of state for presidential affairs, told reporters after meeting the Security Council delegation in Khartoum.
The southern army (SPLA) accused the north of shelling villages and said it had withdrawn its forces from Abyei town after the north moved in.
"We call on the United Nations to protect civilians," said southern army (SPLA) spokesman Philip Aguer. "We are worried about our troops."
The White House condemned the north's military operations in Abyei as "disproportionate and irresponsible" and urged northern and southern leaders to meet and negotiate a settlement.
The U.S. envoy to the United Nations, Susan Rice, speaking in Khartoum, called the escalation in Abyei "quite dangerous."
The 2005 peace deal also promised Abyei residents their own referendum over whether they wanted to join the north or the south. But that vote never took place after both sides failed to agree over who was qualified to vote.
Reporting by Ulf Laessing; editing by Andrew Heavens