Provisional results released on 94% of Wednesday's ballot gave the ANC 67% of the vote, securing its dominance 12 years after the demise of apartheid.
The main opposition Democratic Alliance trailed a distant second with 14.9%, and the Zulu-dominated Inkatha Freedom Party was in third place with 7.4%.
Final results are due on Saturday.
Adam Habib of the respected Human Sciences Research Council attributed the ANC's victory to the "failure of the opposition to capitalise on the growing discontent and the lack of a credible opposition".
Voter apathy was marked in the poor township of Khutsong, near Johannesburg, where residents boycotted the vote.
Khutsong was one of several areas to be rocked by protests over the lack of improvement to basic services such as housing, electricity, roads, sanitation, water supplies, schools and health facilities.
Habib asked: "The big question is, will the ANC see their victory as an affirmation of their policies, or will they be humbled by the reaction of places like Khutsong and go back to the drawing board to re-shape their policies?"
Analyst Paul Graham from the Institute for Democracy in South Africa also interpreted the results as a victory by default.
Residents of the poor town of
Khutsong boycotted the poll
"The opposition parties just have not managed to produce a message or a style of leadership which really resonates with township people," he said.
"The choice of the majority is 'Vote for the ANC or don't vote,'" he added.
Steven Motale, political editor of The Citizen daily - which has an overwhelmingly black readership - said many people did not vote as a silent protest.
"How do you convince a person, who has been voting since 1994, to vote again when 12 years down the line such an individual is still unemployed, still lives in a shack and is still using the bucket system (pit latrines)?" he asked.
There has also been growing anger over the ANC's failure to live up to its ambitious pledges of providing decent housing and basic services to millions of impoverished people, mainly blacks.
Unemployment stands at 26%, and more than half of the country's 46 million people live in poverty.
The ANC trumpets the fact that more than 1.5 million households have moved from shacks to subsidised brick homes with a bathroom since the end of apartheid, but more than 5.6 million families still live in abysmal conditions.
"How do you convince a person, who has been voting since 1994, to vote again when 12 years down the line such an individual is still unemployed, still lives in a shack and is still using the bucket system (pit latrines)?"
Political editor, The Citizen daily
The Sowetan, another prominent black daily, sounded a warning note on Friday to South African President Thabo Mbeki, urging him to "crack the whip".
"More failure of the local government will indict his leadership," it said in a scathing editorial, adding: "Our people cannot wait for empty promises ... They need local government that is responsive. It is time to act."
The ANC's image has also been tarnished by bitter internal feuding after Mbeki fired his popular deputy president, Jacob Zuma, who is now facing corruption and rape charges.
Zuma had hitherto been viewed as Mbeki's successor.
The influential Mail and Guardian weekly on Friday said Mbeki had taken note of the discontent and was "putting in place a battery of measures to fix local government, the ANC's Achilles heel."
The ANC has sacked close to two-thirds of the councillors elected in 2000, and the newly elected representatives will work under a pledge to live among their local communities and to be scrupulously honest.