The launch came after northern and southern leaders agreed they would form a "soft border" allowing the free movement of trade and nomads between their territories in the event of separation, as part of a framework agreement to resolve a list of disputes between the two sides.
The referendum on whether the oil-producing region should declare independence, scheduled for Jan. 9, is the climax of a 2005 peace deal that ended decades of north-south conflict -Africa's longest civil war that was fought over ethnicity, religion, ideology and oil and that killed two million people.
