JUBA

Registration centres for a referendum on potential south Sudanese independence have opened peacefully, officials said on Tuesday, but warned that some outside the south are staying away due to fears of intimidation or risk of fraud.

"All the 2,625 registration centres in the south except two were operational, and those will open in coming days," Aleu Garang Aleu, spokesman for the Southern Sudanese Referendum Bureau, which is running the vote in the south.

"There were no reports of violence, no complaints of interference and there was a high turnout in the south," he said, adding that exact figures were still being gathered from remote centres.

The process was kicked off by southern President Salva Kiir on Monday. He registered at a Juba centre outside a memorial to John Garang, who led the mostly Christian south to a 2005 peace deal that ended a 22-year war with the north before dying in a helicopter crash.

The referendum, part of the 2005 deal that also created a power-sharing government with Kiir as vice president to Sudanese President Omar al-Bashir, is viewed as a gateway to freedom in the south.

In the north, however, turnout in the 165 centers was far lower however, Aleu said.

"They have a fear of intimidation there; they do not want to be identified," he said. "We got a report that in one centre, there was just one person registered."

In addition, Aleu said there was a growing concern amongst diaspora populations, who are able to register in neighbouring Uganda, Kenya, Ethiopia and Egypt, as well as in Australia, Britain, the United States and Canada.

"We have got reports that there is a lot of chaos emerging," said Aleu, referring to southerners voting outside Sudan.

"In Canada, for example, southern Sudanese are boycotting to register simply because they are not sure they will cast their vote when the time for referendum comes," he added.

Some were concerned at the expense of travelling long distances to register and then vote.

In addition, while the intergovernmental International Organisation for Migration (IOM) is assisting the registration process, Aleu said some were concerned it was not able to correctly identify who is eligible to vote.

Many are fearful the IOM "does not have the ability to determine who southern Sudanese are, so people can claim to be southern Sudanese when they are not," said Aleu.

While a simple majority of 50 percent plus one vote is needed to decide either option, the vote will only be valid if 60 percent of registered voters turn out.

About five million south Sudanese are eligible to vote, including an estimated 500,000 to two million abroad, according to UN estimates.

Registration offices will remain open until December 1.

The vote is to be held on the same day as a referendum in the oil-rich Abyei region, with voters there choosing whether to stay with the north or go with the south.