The oil-rich border area remains disputed between Sudan and South Sudan . In a statement released on Monday, the U.N. Security Council said it was "gravely concerned" about reports of violence in Jonglei state. The oil fields account for about half of Sudan 's oil production .
The oil-rich border area remains disputed between Sudan and South Sudan . Sudan claims the oil fields in the town of Heglig . The oil fields account for about half of Sudan 's oil production .