|About four million voters have registered for the referendum that may lead to the partition of Sudan [Ranjit Bhaskar]
Polling stations have closed on the first day of voting in Southern Sudan's week-long referendum on secession.
The atmosphere was festive in the southern capital Juba on Sunday, with voters queueing for hours outside polling stations.
"The turnout was emotional," Chan Reec Madut, who heads the South Sudan Referendum Bureau, said.
"We have never witnessed this kind of turnout before, even during the election," he said, referring to last April's presidential, parliamentary and state elections.
"There is singing, there is dancing, this is a day like no other in the history of the people of south Sudan."
He said the polling would continue as scheduled on Monday.
A total of 3.9 million southerners have registered for the self-determination vote that may lead to the partition of Africa's largest country.
They came in their thousands on the first day itself to participate in an event that matters to them deeply. They were in a hurry and impatient.
Salva Kiir, the president of Southern Sudan, cast his ballot in Juba in the morning and appealed to impatient voters to spread the voting across the scheduled seven days, after having waited for more than 50 years to choose their own destiny.
"This is the moment you have been waiting for," he told crowds outside the polling station.
"Even if you cannot vote today, you have six more days to vote."
Nhial Wei, a young student in the south, said he was proud of the moment. "But we should not count our chickens before they hatch," he said, alluding to the challenges that lie ahead for this would-be young nation.
About 1,400 international observers are deployed across Sudan to see firsthand that the referendum passes off without any incident.
Prominent among foreign poll observers are Jimmy Carter, the former US president, and Kofi Annan, the former UN secretary-general.
Visiting a polling station at the St Bakitha Kator Primary School in Juba, both Carter and Annan said they were so far happy with conduct of the poll and the enthusiasm shown by the people.
Al Jazeera's Casey Kauffmann meets southerners
who are returning to south Sudan to vote
"People have had enough of war. They want to avoid conflict," Annan said.
He told Al Jazeera that the Sudan People’s Liberation Movement (SPLM), the ruling party in Southern Sudan, had plenty of experience, unlike other armed groups that transform into governing parties.
"They have to learn from the mistakes of others and hope not to repeat them," Annan said.
Vote counting will be done on a daily basis and results will be displayed at individual centres. While the preliminary results will be announced from Juba, the final result will be announced in the capital, Khartoum.
Polling stations have been set up in other regions of Sudan for southerners living there, and 116,00 people have registered to cast their ballots in northern states.
Al Jazeera's Mohammed Adow, reporting from Khartoum in the north, said voting there took off to a slow start.
"There were no queues. Most of the 70 polling stations in the capital have more polling officials and observers than voters," he said.
"Officials say the knowledge that they have six more days to vote might be keeping voters away during the first day of the historic polls."
Violence in Abyei
Hours after voting started, deadly clashes were reported in Abyei, the border region which is claimed by both the north and the south. Abyei residents are not voting in the south's referendum.
Officials said the deadly violence involved the Arab Misseriya nomads, loyal to the Khartoum government in the north, and the Dinka Ngok tribe, which is associated with the south.
Al Jazeera's Mohammed Vall, reporting from Abyei, said clashes in the area had been going on since Friday.
"The latest news we have is that six people from the Misseriya side have been killed when they clashed with armed policemen from the Dinka side, belonging to the SPLM," he said.
"According to our source, Misseriya people are getting ready for more clashes by way of revenge."
He said leaders from both sides have met to calm down to situation, and make sure the unrest does not escalate into "all-out war".
A referendum on whether Abyei should stay part of the north or join the south had been scheduled to take place in parallel with the secession vote in the south, but it has been delayed.
In Sudan's turbulent history, a previous vote on independence was cancelled after being scheduled to be held in 1953.
Sudan's British and Egyptian colonisers had promised the people a referendum to choose between an independent Sudan and a union with Egypt. The narrow nationalist movement played its colonisers against each other and declared independence unilaterally in 1956 through a unanimous parliamentary vote.
The northern parliamentarians had persuaded the small bloc of reluctant southern parliamentarians that their region’s autonomy and interests would be given due consideration. But after two years they rejected autonomy for the south.
“That was the outcome of a tradition of exclusionary politics in which the people were never consulted by the elite. This time they did and the populace grabbed the opportunity," Angelo Lokoyome, the co-ordinator for Justice and Peace at the Catholic archdiocese of Juba, said.