On the second day of a week-long referendum on independence for southern Sudan, deadly clashes have broken out.
Authorities in the contested Abyei region say at least 23 people have died in battles between tribespeople and Arab nomads.
Southerners are expected to vote to split from the mostly Muslim north.
Analysts have said Abyei is the most likely place for north-south tensions to erupt into violence during and after the vote.
The referendum is the climax of a troubled peace deal that ended decades of civil war.
Voting has also been taking place in Sudanese communities around the world.
A group calling itself “The Lost Boys from Sudan” boarded a bus in Philadelphia and headed for Virginia to cast their ballots.