South Africans have voted resoundingly to extend the ANC's 20-year rule, ignoring leadership scandals and economic malaise in a wholesale display of loyalty to the party once led by Nelson Mandela.
Final results were expected on Friday, but with about three-quarters of the ballots counted, the ANC had garnered a thumping 63 per cent of the popular vote, spelling a parliamentary majority big enough to hand embattled President Jacob Zuma a second five-year term.
ANC spokesman Jackson Mthembu said the 102-year-old party - which has held power since helping to end apartheid in 1994 - would ultimately receive "an overwhelming mandate" from voters.
The ANC's status as the party of liberation was drilled home by the recent 20th anniversary of democracy and the outpouring of emotion that accompanied the death of former president Mandela in December.
But with 63 per cent, it would still fall short of the two-thirds majority needed to amend the constitution and will see its winning margin reduced for a second consecutive election, down from 66 per cent at the last poll.
Meanwhile the main opposition party, the centrist Democratic Alliance (DA), made rapid gains, boosted by a strong urban turnout.
It's share of the vote rose to 23 per cent, up from 17 per cent at the last election in 2009, according to the incomplete results, and looked set to top the polls in Johannesburg and Cape Town.
DA leader Helen Zille told AFP early on Thursday that she expects the final tally to remain at 23 per cent.
"We'll see how it goes, of course we hope it will be more. We did as much as we could," she said.
Julius Malema's populist Economic Freedom Fighters (EFF) gained five per cent of the vote, less than a year after the party was formed.
Both DA and EFF support has been bolstered by a series of scandals surrounding Zuma and frustration at rampant poverty and poor public services.
Casting his ballot in his home village of Nkandla, Zuma predicted the "results will be very good", but conceded the campaign had been "very challenging".
Zuma has been a lightning rod for criticism of the ANC.
He came to office facing rape and corruption charges, and has most recently been pilloried for spending $US23 million ($A24.89 million) of taxpayer money to upgrade his private home.
But voters appeared to put storied party before sullied president.
"When it comes to national elections the vast majority of ANC supporters decide that their loyalty to the organisation is greater than their loyalty to its current leadership," said political commentator Steven Friedman.
A record 25 million voters registered for the elections amid mounting anger over joblessness, inequality and corruption.
Turnout is said to be over 70 per cent, including hundreds of thousands of "born free" South Africans, who were registered to vote in a general election for the first time.
The ballot was marred by isolated incidents of violence, including the killing of one ANC member at a polling station in KwaZulu-Natal province.
Pansy Tlakula, chairperson of the Independent Election Commission, said a number of complaints were being investigated.
But, she added, "we believe the credibility of the election has not been affected".
