By Ulf Laessing
KHARTOUM (Reuters) - Sudan's northern army accused the South's forces on Friday of attacking a convoy in the contested Abyei region, and threatened to retaliate, escalating a dispute that looms over plans for the South's independence.
The South's SPLA army denied responsibility for the attack, which the United Nations said had taken place on a convoy of northern troops escorted by U.N. peacekeepers under a deal for both sides to withdraw forces from the disputed territory.
The overnight attack and the North's threat to retaliate raises the prospect of more violence in Abyei, an oil-producing border region claimed by both sides, which has emerged as the main source of dispute before the South's independence.
South Sudan is due to become independent on July 9 after a vote in January but tensions have risen in Abyei where both sides have built up forces, according to the United Nations.
"Abyei is now a war zone," said Sadiq Amer, deputy head of northern intelligence and security forces, adding that at least 22 soldiers had been killed in what he called an "aggression" of southern forces against a convoy of around ten vehicles.
"The troops were ambushed without any warning," he told reporters in the capital Khartoum, adding the army was ready to retaliate if ordered to do so.
The United Nations did not identify the attackers but said the ambush took place in Dokura, an area it said was controlled by southern police forces.
A spokeswoman for the U.N. Mission in Sudan (UNMIS) did not confirm the northern death toll, saying only two Sudanese soldiers and one peacekeeper had been injured.
"We are still investigating," she said.
Under a deal to ease tension, the North and South agreed to withdraw all of their forces from Abyei except for a special joint force made up of units from both sides. The pullout was supposed to be completed this week.
The South's SPLA said confusion between the joint force and the convoy may have been responsible for the shooting.
"It is not true that SPLA attacked. That situation needs a proper investigation," said SPLA spokesman Philip Aguer. "We have reports there was confusion between JIU (the joint force) and the convoy and it is not clear who shot first.
"The only SPLA in the area are part of the JIU. One SPLA commander was even in the convoy," he added.
The mainly Muslim North and the South, where most people are Christian or practice traditional beliefs, fought for decades in a civil war that killed an estimated 2 million people.
The war was ended by a 2005 peace deal that led to the referendum on southern independence, but the sides continue to clash over Abyei, which also contains fertile grazing land.
Earlier this month, at least 14 people were killed in clashes between northern and southern forces in Abyei. Both sides blamed each other for starting the violence.
The SPLA's Aguer said that three SPLA soldiers were killed by northern forces on May 15 as they were leaving the area under the withdrawal agreement.
Last month, Sudan's President Omar Hassan al-Bashir said he would not recognize the South's independence unless it gave up a claim on Abyei, made in the south's draft constitution.
Abyei residents were also supposed to have a referendum in January over whether to join the north or south. Disputes over who could vote derailed that ballot and talks over the status of the region have stalled.
(Additional reporting by Jeremy Clarke in Juba, Sudan; Writing by Dina Zayed in Cairo and Ulf Laessing in Khartoum; Editing by Peter Graff)