U.S. diplomats have praised the vote on an independence referendum for southern Sudan, which has had good turnout despite a deadly attack on Monday.
Voters in oil-rich southern Sudan are casting ballots during a week-long voting period on whether or not to declare independence from the north. The referendum is one of the requirements of a 2005 peace agreement that ended decades of civil war in Sudan.
U.S. Ambassador Princeton Lyman on Tuesday called the vote "a courageous act," saying he is impressed with the willingness of the Sudanese people to make a very tough decision. Assistant Secretary of State for African Affairs Johnnie Carson reiterated the U.S. commitment to helping Sudan prosper, whether or not it divides.
Polling stations are to remain open through Saturday, despite reports of clashes. A southern Sudanese official says Arab tribesmen ambushed a bus carrying voters in South Khordofan state Monday, killing 10 people and wounding 18 others.
The bus was carrying southerners who live or work in the north to polling stations in their original home districts.
At least 36 people have been killed in recent clashes, with fighting heaviest in the disputed Abyei district, at the border between northern and southern Sudan.
A pro-independence vote in the south is widely expected. From Khartoum, Sudanese President Omar al-Bashir has pledged to accept the results and help the south regardless of the outcome.
Prominent observers from around the world, including former U.S. president Jimmy Carter and former U.N. secretary-general Kofi Annan, are in Sudan for the referendum. Nearly four million people are registered to vote. Preliminary results are expected next week.