Sudanese forces claimed to be advancing on Heglig and that the situation would be dealt with "within hours."
There was no clear casualty toll for the Sudanese forces, but a Southern official put the number of dead at 240 killed and hundreds wounded.
It had been accused of assisting Sudanese forces in an ethnic cleansing campaign against villagers near its oil fields.
Sudanese forces confirmed that they found the bodies of 90 rebels and had spotted dozens more strewn outside the city limits.
It was attacked by Sudanese forces during 2003/2004 in the Darfur conflict.
He was appointed Commander in Chief of the Sudanese armed forces at independence.
The real campaign started when Sudanese forces open the fire against Bentiu, and make 5 casualties.
Unprepared to fight against a real army, the Sudanese forces surrendered or were overwhelmed within the day.
By this time, the Khalifa's Sudanese forces had retained at least 10,000 people.
The Sudanese armed forces used militias to attack civilian populations in the south.