South Sudan returnee train attacked in South Kordofan
A train carrying South Sudanese back home from the north has been attacked by a northern Arab group, leaving one person dead, the UN says.
A UN spokeswoman said the train was attacked by Misseriya gunmen in South Kordofan state on Sunday, although this was denied by a Misseriya leader.
At least 70,000 people have fled recent fighting in South Kordofan, which borders South Sudan.
Tension has been rising ahead of the south's independence next month.
Another 100,000 people have been forced from their homes after fighting in the disputed town of Abyei, near South Kordofan.
Since the end of the 21-year north-south war, some two million southerners have returned home and more are going ahead of the formal declaration of independence due on 9 July.
"A train transport of southern Sudanese returnees going from Kosti to Wau was attacked by Misseriya militia," said UN spokeswoman Hua Jiang.
However, Misseriya leader Mohamed Omer al-Ansary said the attack had been carried out by rebels in the neighbouring region of Darfur, where a separate conflict broke out in 2003.
Northern forces have been accused of bombing parts of South Kordofan inhabited by ethnic Nubans, who largely supported the south during the civil war.
The fighting broke out after pro-southern groups were ordered to disarm after Ahmed Haroun was declared the winner of recent governorship elections.
Mr Haroun is wanted by the International Criminal Court for alleged crimes against humanity committed in Darfur.
Over the weekend, Mr Haroun said the situation was now safe and people have started to return to their homes.
However, human rights group Amnesty International accused the authorities of forcing the displaced to go home despite continuing violence.
The Sudanese air force is accused of carrying out more bombing raids on Saturday.
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.