Figures gathered from state and county referendum officials showed that 2,224,857 votes for independence have already been returned.
That comfortably exceeds the simple majority of 1.89 million votes needed on the 96-percent turnout of the 3,932,588 registered voters.
In Lakes state, centred on Rumbek town, which served as rebel headquarters during a devastating 1983-2005 civil war with the north, 298,216 of 300,444 votes cast were for independence, more than 99.9 percent.
Just 227 opted to remain united with the north -- less than a tenth of one percent -- with the balance made up by blank or invalid ballots.
In Central Equatoria, which includes the regional capital Juba and is the south's second most populous state, 449,321, or 98.2 percent, of 457,452 votes were for secession.
Just 4,985, or barely one percent, voted for unity.
In Juba, a once sleepy town now poised to become the world's newest national capital, cheers and applause rang out as the head of the county's referendum sub-committee, Timon Wani, announced a 97.5 percent majority for independence.
"This is a great result," said Mohammed Lowala, who was among the crowd.
"You cannot get a decision more clear that the south wants to be free than 97.5 percent," he said. "The people of Juba county have spoken for independence and I am sure that the rest of the south will follow."
The tin-roofed office in the centre of Juba that served as a centre for the count had been crammed with officials from early morning double-checking results tallied by hand.
Local resident William Moro said: "We know the result is for separation because that is what everyone wants. But hearing the results announced to make it official will be very exciting -- to have the piece of paper to show the north."
The final result, which will set south Sudan on the path to recognition as the world's newest state in July, is not expected before next month. That will come after the state results have been collated at regional level and added to those of southerners who voted in the north or in eight countries of the diaspora.
If there are no legal appeals, it will be declared on February 7. If there are, it will be a week later.
"We are being methodical to make sure all the rules are respected -- and that takes time, of course," said Aleu Garang Aleu, a spokesman for the Southern Sudanese Referendum Bureau, which is running the vote in the south.
Southern leaders had warned against any premature celebration or triumphalism that might undermine hopes of a "velvet divorce" from the north after five decades of conflict, and life carried on the streets pretty much as usual.
At wooden stockades dotted among the thatched huts and corrugated iron shacks of Juba, herders brought in their goats and long-horned cattle for the night.
Even Juba's main monument, the tomb of veteran leader John Garang who signed the 2005 peace deal that provided for the referendum, was deserted as people heeded the call to await the official results before partying.
It was at a makeshift polling station set up by the tomb that Garang's successor, southern president Salva Kiir, was among the first to vote at the launch of the week-long vote on January 9.
Kiir joined thousands of faithful in going to church last weekend to pay tribute to the estimated two million people who died in the civil war.
"For our deceased brothers and sisters, particularly those who have fallen during the time of struggle, may God bless them with eternal peace," he said.
"And may we, like Jesus Christ on the cross, forgive those who have forcefully caused their deaths."
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