Jacob Zuma joined dancers on stage at the ANC garden party in Johannesburg
African National Congress leader Jacob Zuma appeared before a cheering crowd, as his party headed for a clear victory in South Africa's general election.
Mr Zuma - set to be the next president - said the ANC had put across its policies and people had understood.
With more than 12 million votes counted, the ANC had just under 67%.
But it is still not clear whether the party will retain the two-thirds parliamentary majority needed to push through constitutional changes.
The opposition Democratic Alliance (DA) has about 16% and the Congress of the People - formed as a direct challenge to the ANC - is trailing with 7.6%.
The DA was ahead in Western Cape province, which is currently controlled by the ANC, with almost 50% of the vote.
The ANC is ahead in the eight other provinces, although results are still awaited from the major metropolitan areas.
Wednesday's poll was the country's fourth, and most competitive, general election since the end of apartheid 15 years ago.
Election officials put turn-out at about 77%. Formal election results are not expected until Saturday.
In Johannesburg, crowds of ANC supporters dressed in the party's black, yellow and green attended a celebration rally.
"I would like to thank you for tonight," Jacob Zuma told the crowd, after dancing on stage.
"We went to the voters of this country, talked to them and put across our polices - and they have understood what we are saying," he said.
Parliament will elect South Africa's next president by a simple majority, putting Mr Zuma in line for the post when the new assembly votes in May.
Mr Zuma, a populist who spent 10 years in prison during the apartheid era for ANC membership, faces challenges including a struggling economy and soaring violent crime.
Charges of corruption against the 67-year-old were dropped just two weeks before the poll after state prosecutors said there had been political interference in the case.
'Doubled our numbers'
The election commission said it was pleased with the peaceful way in which the poll was conducted.
Leaders of the rival parties said that the early results brought some positive news.
DA leader Helen Zille said her party was pleased. "We are just above 50% in the Western Cape, that is what we were hoping for because it means we have doubled our numbers since last time," she said.
The Cope leader, former Bishop Mvume Dandala, told the BBC that the party did not see the result as a rejection. "We are saying that we have been given a critical mass upon which to build," he said.
Cope was formed by ANC dissidents who supported former President Thabo Mbeki, who resigned last year after losing a power struggle with Mr Zuma.
Analysts say Cope's emergence energised the early stages of the election campaign but the party's popularity seems to have diminished in recent weeks.
It is thought that Cope and the DA could enter into a coalition after the election, presenting a real threat to the ANC's continued dominance of South Africa.