Sudan: UN probes clashes in oil-rich South Kordofan
The UN is investigating clashes that have broken out in Sudan's oil-producing state of South Kordofan.
The volatile region is on the northern side of the border with South Sudan but is home to many who fought for the south in Sudan's long civil war.
Tensions have been rising ahead of South Sudan's formal independence from the north in July.
Flashpoint issues include the exact position of the common border and the fate of the disputed Abyei region.
UN officials in Sudan said gunmen looted weapons from a police station in Kadugli, South Kordofan's capital. Hours later there was a gunfight in a village about 48km (30 miles) from Kadugli.
It was not clear if the two events were connected.
South Kordofan is controlled by the north but is home to many southern-allied soldiers. The state was on the front lines during Sudan's protracted civil war.
The governing party in South Sudan, the Sudan People's Liberation Movement (SPLM), blamed northern military forces for the clashes.
They said the fighting involved northern soldiers rebelling against orders to disarm the southern-allied soldiers.
Analysts say the Khartoum government in northern Sudan is trying to assert its authority over the border regions ahead of South Sudan's formal declaration of independence, scheduled for July.
A January referendum on its independence was the result of the 2005 peace deal that ended the civil war.
On 21 May, northern troops and militias entered the disputed border region of Abyei. Tens of thousands of people have fled as homes have been looted and burned.
Khartoum has ignored a call from the UN Security Council to withdraw its troops from Abyei.
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.