Analysts cite Abyei as the most likely place for north-south tensions to erupt into violence during and after the vote, the climax of a troubled peace deal that ended decades of civil war.

The south is expected to split from the mostly Muslim north, depriving Khartoum of most of its oil reserves.

Residents of the central Abyei region were promised their own referendum on whether to join the north or the south but leaders could not agree on how to run the poll and the vote did not take place, as planned on January 9.

Leading members of Abyei's Dinka Ngok tribe, linked with the south, accused Khartoum of arming the area's Arab Misseriya militias in clashes on Friday, Saturday and Sunday and said they were expecting more attacks in days to come.