KHARTOUM Sudan's president on Tuesday refused to withdraw troops from the disputed Abyei region they seized over the weekend, defying international calls for them to pull out and raising the stakes in a standoff with the south.
"Abyei is northern Sudanese land," Omar Hassan al-Bashir said in a speech, adding he had given the green light to the northern army to respond to any "provocation" by the south which also claims Abyei and plans to secede in July.
Sudan's northern army moved tanks into Abyei town, the border area's main settlement, on Saturday, sparking an international outcry and forcing thousands to flee.
Analysts are watching how the south will react, fearing further north-south fighting over Abyei, which has oil and grazing land, could reignite a full-blown conflict that would disrupt the already fragile region.
North and south Sudan fought for decades before a 2005 peace deal that also allowed southerners to vote overwhelmingly for independence in a referendum in January.
The United Nations said on Tuesday it has asked south Sudan to investigate separate attacks on U.N. peacekeepers in Abyei last week by what appear to have been southern security forces.
Such attacks, the U.N. said, amount to war crimes.
"The available information and eyewitness accounts describing the assailants, including their uniforms, strongly suggests that the attackers were members of the southern Sudan police or military forces," U.N. spokesman Martin Nesirky told reporters in New York.
Khartoum accused the south of ambushing northern troops traveling in a convoy with U.N. peacekeepers on May 20 in the Abyei region. The south denied carrying out the attack.
Earlier on Tuesday in Khartoum, Sudan Cabinet Affairs Minister Luka Biong, a southerner, told Reuters he was resigning in protest at the northern seizure of Abyei.
"These are real war crimes. I have never seen such suffering. Houses are burned in Abyei town and south of it," Biong said.
U.N. officials said between 15,000 and 20,000 people fled Abyei, many heading to Agok, just over the southern border.
"We are concerned ... about the grave humanitarian consequences of what's transpired in Abyei. There have been horrific reports of looting and burning," said Susan Rice, U.S. ambassador to the U.N., visiting the southern capital Juba.
North Sudanese officials said their army moved in to clear out southern soldiers who it said had broken agreements by entering the area. The south denies this.
The African Union said former South African President Thabo Mbeki had met Sudan's President Bashir and southern President Salva Kiir to try and resolve the crisis.
Abyei remains the most contentious point in the build-up to the secession of the south, the source of 75 percent of the country's 500,000 barrels a day oil production.
The 2005 deal also promised Abyei residents their own referendum over whether to join north or south, but that did not take place as neither could agree who was qualified to vote.
The peace deal created a coalition government dominated by Bashir's National Congress Party and the former southern rebel Sudan People's Liberation Movement (SPLM), headed by Kiir. Both were also allowed to keep their own armies.
The coalition government is due to be dissolved on the secession of the south which currently has its own semi-autonomous government.
(Additional reporting by Ulf Laessing in Khartoum, Jeremy Clarke in Juba, Louis Charbonneau at the United Nations, Barbara Lewis in Geneva, Wangui Kanina in Nairobi and John Irish in Paris; Editing by Andrew Heavens)