Renewed fighting on Sudan border near disputed oilfield
Fighting has broken out on the border between Sudan and South Sudan, shortly after the South pulled out of a disputed border town.
South Sudanese military officials say they repulsed ground and air attacks.
Sudan confirmed there had been clashes, which come after 10 days of fighting over the oilfield town of Heglig.
On Monday, a Sudanese warplane dropped bombs near the South Sudanese border town of Bentiu, killing at least one person, eyewitnesses said.
Satellite pictures of the Heglig area released on Sunday suggest key oil installations were badly damaged in the fighting and are no longer operating.
The pictures were analysed by the US-funded Satellite Sentinel Project (SSP), which says it is impossible to know who was responsible for the damage.
Sudan and South Sudan have accused each other of attacking oil facilities. On Friday, South Sudan said it was withdrawing from Heglig, while Sudan said it forced out the South Sudanese troops.
Access to the disputed border region around Heglig is limited, making it difficult to verify what is happening in the area.
The renewed fighting has been taking place to the south of the Heglig oilfields, although it is unclear which side of the disputed border it is happening.
Sudan military officials said its forces had repulsed a major rebel attack.
The BBC's James Copnall, who is in Bentiu, says the fighting makes it clear that tension has not eased, and also underlines that all-out war is still a possibility.
He says South Sudan is building up its troops near the border, and is assuming that Sudan is doing the same.
Monday's reported bombing raid by Sudanese planes targeted a bridge between Bentiu and the nearby town of Rubkona.
Eyewitnesses said one child had died and market stalls were on fire.
South Sudan's deputy head of military intelligence, Mac Paul, described the bombing as a "serious escalation" and a "provocation".'Runway lengthened'
The satellite pictures provided by SSP suggest that the oil industry has been deliberately targeted in the earlier fighting.
One picture appears to show an oil collection point at the end of two pipelines has been destroyed, leaving charred wreckage over a wide area.
SSP says it is impossible to know whether the damage was done by aerial bombing or ground attacks.
Others show tanks, smoke rising from explosions that are consistent with aerial bombing, and cratering.
There are also pictures showing that the Sudan Air Force runway in South Kordofan has been paved and lengthened to allow Antonov bombers to land there.
SSP, which was set up to campaign against the return to full-scale civil war between the two countries, used pictures from DigitalGlobe satellites, which were analysed by the Harvard Humanitarian Initiative.
SSP receives funding from the Not on Our Watch project, founded by US activists including the actors George Clooney, Brad Pitt and Matt Damon.
On Friday, South Sudan said it would withdraw from Heglig, while Sudan said its forces had re-taken control of the area.
The area north of the disputed border provides most of of Sudan's oil output, and is a crucial part of its economy.
Meanwhile on Monday the South Sudan President Salva Kiir is travelling to China for an official visit, the AFP news agency reports.
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.