Sudan detains foreigners in disputed area
Sudanese officials say four foreigners have been detained in the sensitive Heglig oilfield area, scene of recent fighting with South Sudanese forces.
The four - from the UK, Norway, South Africa and South Sudan - were in an armoured vehicle and engaged in "suspicious activities", they said.
The group was flown to the Sudanese capital for "further investigations".
Sudanese TV said the men are suspected of aiding South Sudan, a charge rejected by a Southern official.
"That is rubbish and just a lie," said Philip Aguer, South Sudan army spokesman, quoted by Reuters news agency.
A United Nations spokesman in South Sudan told the agency that a staff member was among the group taken to Khartoum.
An official with Norwegian People's Aid said one of its members was also in the group.
Mechem, a South African de-mining company told Reuters news agency that two of its employees, a South African and a South Sudanese, were among those arrested.
"We are working on a UN de-mining contract and our employees have full UN immunity," Mechem's chief executive, Ashley Williams, said in a statement emailed to Reuters.'Military backgrounds'
"We captured them inside Sudan's borders, in the Heglig area, and they were collecting war debris for investigation," Sudan army spokesman Sawarmi Khaled Saad said at Khartoum airport.
All four had military backgrounds, he added.
The men, who were not further identified, were paraded before the press but not allowed to talk.
One man was wearing the T-shirt of a Norwegian non-governmental organisation, while another wore one with the logo of a South African de-mining group.
The British embassy in Khartoum said it was in contact with the Sudanese authorities and was looking into the matter.
South Sudan's ambassador told the BBC he was checking with his government.
The BBC's James Copnall in Khartoum says the arrests underline the continuing tensions between Sudan and South Sudan.
Clashes began in April when the Heglig oilfield was occupied by forces from South Sudan.
They left about a week ago, after holding the area for 10 days.
Our correspondent says tension is still extremely high, and Sudan has been accused of carrying out a number of air raids on South Sudan this week. It denies the charges.
South Sudan became independent from Sudan after a civil war that lasted two decades and in which an estimated 1.5 million people were killed.
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.