Sudan's Abyei dispute: 'Shots fired' at UN helicopters
Shots have been fired at UN helicopters in the disputed Sudanese region of Abyei, the UN says.
A UN spokesman told the BBC that 14 shots had been fired at four helicopters but none had been hit.
Tension is high in Abyei, which was seized by northern troops at the weekend - a move condemned by the UN Security Council.
The region is also claimed by South Sudan, which is due to become independent in July.
Analysts fear the the dispute could reignite the north-south conflict, in which some 1.5 million people were killed.
The status of Abyei was left undecided in the 2005 peace deal and a referendum, due in January, on whether the area should be part of the north or south has been postponed indefinitely.
Aid workers say some 40,000 people have fled the fighting around Abyei - mostly southerners, heading further south.
A southern official said many were in a "miserable situation".
The UN believes militiamen from the Misseriya ethnic group were responsible for shooting at the helicopters.
The Misseriya are northern nomads and one of two groups to claim Abyei, along with the southern Dinka Ngok people.
The two groups often clash as their herds of cattle look for water and pasture.
The Misseriya were armed by Khartoum and used to attack the south during the civil war.
The BBC's James Copnall in Khartoum says the Misseriya are also being blamed for what the UN calls "burning and looting" in Abyei.
Reports suggest many Misseriya have arrived in the town since the northern armed forces took control of it on Saturday.
A Misseriya leader, Sadig Babo Nimr, told the BBC the accusations were "fallacious nonsense" and "against logic".
Northern army primed
The Satellite Sentinel Project has released satellite images of burnt huts and says they provide evidence of war crimes.
UN human rights chief Navi Pillay has said she has received reports that northern forces had been shelling and bombing civilian areas.
The United Nations and the US have called on the northern troops to withdraw from Abyei.
But President Omar al-Bashir said he would not withdraw troops from the region and insisted that the area belonged to the north.
He added that his army would respond to any possible "provocation" from the army of South Sudan.
Northern troops seized the territory after southern forces had ambushed a convoy of its forces in the area, killing 22 people.
Referring to US warnings that the seizure could jeopardise billions of dollars of possible debt relief and moves to drop sanctions, he said: "Sudan is not greedy for the carrot of America, and does not fear from its stick."
The US envoy to Sudan, Princeton Lyman, has warned that the takeover of Abyei puts at risk moves to cancel billions of dollars worth of Sudan's debt.
He also said that Washington would find it difficult to remove Sudan from its list of state sponsors of terrorism unless troops were withdrawn from Abyei.
Under these sanctions Sudanese companies are banned from using US currency - a major obstacle to international trade.
The US has previously suggested that a peaceful transition to independence for the south and a negotiated solution to the separate conflict in Darfur could normalise relations.
Both Sudan and the South are reliant on their oil revenues, which account for 98% of South Sudan's budget. But the two countries cannot agree how to divide the oil wealth of the former united state. Some 75% of the oil lies in the South but all the pipelines run north. It is feared that disputes over oil could lead the two neighbours to return to war.
Although they were united for many years, the two Sudans were always very different. The great divide is visible even from space, as this Nasa satellite image shows. The northern states are a blanket of desert, broken only by the fertile Nile corridor. South Sudan is covered by green swathes of grassland, swamps and tropical forest.
Sudan's arid north is mainly home to Arabic-speaking Muslims. But in South Sudan there is no dominant culture. The Dinkas and the Nuers are the largest of more than 200 ethnic groups, each with its own languages and traditional beliefs, alongside Christianity and Islam.
The health inequalities in Sudan are illustrated by infant mortality rates. In South Sudan, one in 10 children die before their first birthday. Whereas in the more developed northern states, such as Gezira and White Nile, half of those children would be expected to survive.
The gulf in water resources between north and south is stark. In Khartoum, River Nile, and Gezira states, two-thirds of people have access to piped drinking water and pit latrines. In the south, boreholes and unprotected wells are the main drinking sources. More than 80% of southerners have no toilet facilities whatsoever.
Throughout the two Sudans, access to primary school education is strongly linked to household earnings. In the poorest parts of the south, less than 1% of children finish primary school. Whereas in the wealthier north, up to 50% of children complete primary level education.
Conflict and poverty are the main causes of food insecurity in both countries. In Sudan, many of the residents of war-affected Darfur and the border states of Blue Nile and South Kordofan, depend on food aid. The UN said about 2.8m people in South Sudan would require food aid in 2013. The northern states tend to be wealthier, more urbanised and less reliant on agriculture.