Sudan 'bombs refugees' in South Sudan's Unity state
South Sudanese officials have condemned Sudan after an aerial bombardment of a refugee camp in their territory.
The BBC's James Copnall was at the Yida camp in oil-rich Unity State, which borders Sudan, when it was bombed.
Local official Miabek Lang said at least 12 people had been killed and 20 wounded.
The Sudanese military, which has been fighting rebels in areas near South Sudan, has denied the claims.
Our reporter says he arrived at the camp at about 12:00 GMT on Thursday as a second round of bombs hit.
He says that just as a UN helicopter, carrying food aid, settled on to a makeshift landing zone at the camp, there was a deep and terrifying thud of a nearby explosion.
A large plane was spotted heading to the north, our reporter says.'Completely false'
Several residents of the refugee camp told him it was an Antonov plane, often used by the Sudanese government as a makeshift bomber.
The refugees said the plane had circled before launching two bombing raids.
Five bombs were dropped, of which four exploded, they told our correspondent.
At the scene
Just as a UN helicopter settled on to a makeshift landing zone, there was a deep and terrifying thud of a nearby explosion. A large plane glinting silver against the sun was spotted heading to the north.
It was identified by several residents of the refugee camp as an Antonov, a plane that is feared here because the Sudanese government has often used it as a makeshift bomber.
The refugees said the plane had circled, then launched two bombing raids. They said five bombs were dropped, of which four exploded.
The unexploded bomb, a flat grey sphere, had hit a tree, and came to rest in soft earth just outside a school. Another bomb sparked a small fire, and left a crater in the earth.
Our reporter says he did not see any casualties, but Mr Lang, the commissioner of Pariang county in Unity state, said that 12 people had been killed and the death toll could rise.
Incidents like this, and both sides' belief that the other is sponsoring rebels on their territory, are contributing to a rapidly deteriorating relationship between Sudan and South Sudan, he says.
Thousands of people who have fled fighting in Sudan's South Kordofan region have crossed the border to take refuge at the Yida camp.
Sudan's army has often been accused of bombing South Kordofan, where it is facing a rebellion from pro-southern groups.
Our reporter says there is talk that rebels use the camp to rest before returning to South Kordofan to fight.
The refugees are, however, furious with Sudan's President Omar al-Bashir over the bombings, he says.
The governor of Unity State, Taban Deng, said Mr Bashir should be held responsible.
"Why does Omar Bashir do this? He has a lot to answer," Mr Deng said.
However, Sudan Armed Forces spokesman Sawarmi Khaled Saad vehemently denied any links to the raid.
"This information is completely false. We didn't bomb any camps or any areas inside the borders of South Sudan," he told the AFP news agency.
"What is going on in South Sudan belongs to the southerners. We don't have any links to this."
The South Sudan Liberation Army rebel group is active in Unity State - it denies claims that it is working for Khartoum in order to destabilise its neighbour.
South Sudan gained independence in July under a peace deal which followed decades of north-south conflict.