|The UN says 180,000 southerners have returned from the north since November last year [AFP]
A handful of South Sudanese have voted on the final day of a week-long referendum on whether to split from the north of the country.
Polls closed on Saturday after the 60 per cent voter turnout threshold set for the referendum to be valid was achieved on Wednesday after just four days of polling.
"The voting has now finished. The ballot boxes are locked away safely. The count will start after a break," Joseph Kharin, a referendum commission official, told the AFP news agency.
UN helicopter crews will assist organisers in picking up ballot papers from the remote countryside of a vast, underdeveloped region which has just 40km (25 miles) of paved road for an area the size of France and Belgium combined.
"Preliminary results will be announced on January 31st. Those figures will then have to be verified in Khartoum. If there are no appeals, officials say a final result will be announced on February 6," Al Jazeera's Haru Mutasa, reporting, from Juba.
However, overseas voting in Brisbane, Australia, has been extended for several days as a result of flooding in that region.
Observers have said that they are confident that the result will favour secession from the north.
If the planned timeline is adhered to, south Sudan could secede by July.
"They have technically until the 9th of July, [which is] when the comprehensive peace agreement expires," reported Mutasa.
Jimmy Carter, a former US president who is in the country to observe the poll, said he expected that the north would "recognise the results immediately".
"We already know that in the south there's been about an average of 90 per cent [participation] from the stations we've observed and I think they are representative," Carter said.
In the few centres where he had seen counting under way, he said, the votes "were practically unanimous in favour of separation with only a few ballots to the contrary".
The referendum marks the culmination of the 2005 comprehensive peace agreement, which ended a civil war in the country.
A senior official of Sudanese President Omar al-Bashir's National Congress Party (NCP) said the north would accept the outcome of the vote even if it was for partition of Africa's largest nation.
Georg Charpentier, the UN humanitarian co-ordinator for Sudan, said a total of 180,000 southerners had returned from the north since November, with more than 15,000 arriving in the week-long polling period alone.
He said the UN was expecting between 500,000 and 600,000 people to arrive by August.
"Obviously the emotions around the referendum have prompted many southerners to come home," he said, speaking at Juba's river port on the White Nile where many of the returnees arrive.
On the streets of the Sudanese capital, Khartoum, there was a sense of rueful resignation that the nearly nine million people of the south were poised to break away - and take with them some 80 per cent of Sudan's oil reserves - leaving the north's 32 million people to go it alone.
"I feel sad," Mustafa Mohammed, a young tax officer, said. "I am not for secession."
Rally in north
Meanwhile, thousands of Sudanese demonstrated in the Nuba mountains in the north, demanding free and fair elections ahead of a planned move toward greater autonomy.
Kauda, a remote mountain town, is a stronghold of the Sudan's People's Liberation Movement (SPLM), the biggest political party in the south, but falls in the northern state of South Kordofan.
Large crowds gathered in the town, chanting anti-government slogans and waving SPLM flags.
The protesters claimed that the election process was not going as planned in their area.
"The government wants to use the old list of voters. But the list does not include all the population here. Many people can't find their names on the list," Sadiq Said, one of the demonstrators, said.
The election is part a "popular consultation" process that many in the area believe will help them achieve independence from the north..