The vast territory has been wracked by violence since southerners voted in January to separate from the north and form a new nation. More than 1,500 people have since died in south-south violence, according to the United Nations.

At least seven rebel militias are at war with the government, the U.N. says. Gun battles between these militias and the army, and tribal warring over cattle, have erupted in nine of the south's 10 states.

South Sudan's internal crisis has been overshadowed by the threat of open conflict with the north, and persistent fighting in the border region in recent weeks has displaced tens of thousands and strained the fragile peace.

Analysts say that even if the north-south peace holds, the new country could still fail if it cannot rein in its internal violence.

Reuters