Sudan: UN peacekeepers attacked in Abyei
Four UN peacekeepers in Sudan have been wounded after their patrol was attacked in the disputed Abyei region along the north-south border.
The UN mission said the attack on its patrol in Goli village, 25km (15 miles) north of Abyei town, was unprovoked.
The BBC's James Copnall says the incident comes at a surprising time.
On Sunday the north and south agreed to remove any unauthorised troops from Abyei, claimed by both sides, which was seen as a positive development.
The UN mission in Sudan, which brokered the withdrawal deal, said the peacekeepers attacked in Goli were from Zambia, and that one of them was in a critical condition.
Abyei is disputed by the Dinka Ngok, a southern ethnic group who are the permanent residents of the region, and the Misseriya, northern nomads who spend part of every year there seeking pastures for their cattle.
Since January there have been a series of bloody clashes between the groups.
They accuse each other using their security forces in the fighting, and of a build-up of troops near Abyei.
Our correspondent in the northern capital, Khartoum, says the fear is that if a solution is not found, Abyei could ignite a new north-south civil war.
South Sudan is preparing to secede from Africa's biggest country in July, after 99% of voters backed independence in January's referendum.
A draft version of South Sudan's interim constitution explicitly claims Abyei is in the south.
Last month, President Omar al-Bashir threatened not to recognise the new state if it tried to claim Abyei.
The Abyei region was meant to have its own referendum on whether to join the north or the south in January, but agreement could not be reached on whether the Misseriya could vote.
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.