South Sudan in conflict with Sudan over disputed region
12 April 2012 Last updated at 01:52 BST
There is fierce fighting for a second day between Sudanese and South Sudanese forces in a contested region on their disputed border.
It is reported that South Sudanese forces have taken control of a large oil field in the border town of Heglig, which officially belongs to Sudan.
South Sudan says the assault was a response to ground and air attacks from the north.
The African Union has demanded South Sudan withdraw from the oil field, and there is increasing concern that these clashes could take the region back to all out war.
The BBC's James Copnall from Khartoum.