The United Nations evacuated non-essential staff from the flashpoint Sudanese town of Abyei on Wednesday after deadly fighting erupted between government troops and southern ex-rebels.
"We are very concerned about what is happening in Abyei in the last 24 hours. It is alarming because there is fighting in the centre of the town using heavy weapons," UN spokesman Khaled Mansour told AFP in Khartoum.
"We have evacuated our non-essential staff from Abyei to Kadugli which is standard practice in such situations. The rest of our staff are still there to perform their duties."
A helicopter flew out around 20 people, including about 10 UN personnel, and other aid workers from the small, impoverished town.
The United Nations called on both the Sudanese armed forces and the Sudan People's Liberation Army (SPLA), which fought a two-decade civil war with Khartoum until a 2005 peace agreement, to cease hostilities immediately.
The town lies at the centre of a district on the border between north and south Sudan and its oil wealth is bitterly contested by the two sides.
An impasse over the area is one of the key stumbling blocks that has delayed implementation of the peace deal.
The SPLM and army militia reportedly clashed about 10 kilometres (six miles) north of Abyei on Tuesday. On Wednesday, heavy but sporadic fighting erupted in Abyei itself with guns, grenades and rocket-launchers, punctuated by lulls.
Brigadier General Muntasir Sabier, the army commander in Abyei, told AFP by telephone that one of his soldiers was killed and another wounded.
He said civilians had fled their homes, that there had been shooting next to the hospital and that "half the market" had been burnt in the fighting.
"The town is completely deserted. It is a ghost town," he said. Although the town had been quiet since before dusk, he expected clashes to resume.
Representatives of both sides met international peacekeepers in Abyei and agreed on measures to defuse the tension, Mansour said.
Aid workers speaking to AFP by telephone had no information of any civilian casualties but said at least two soldiers had been killed.
Shops were closed and the streets deserted, they said.
No southern Sudanese officials were immediately available for comment.
The SPLM accuses President Omar al-Beshir's National Congress of failing to implement a special protocol to govern Abyei during a key transition period.
In 2011, Abyei will hold a referendum on whether to retain its special administrative status in the north or be incorporated into the south; and a second one on whether the south should break away as an independent state.
