South Africa's ANC celebrates 100 years at mass rally.

Tens of thousands streamed into a stadium in the scorching central city of Bloemfontein which wraps up weekend celebrations for the African National Congress, which Nelson Mandela led to power after the fall of apartheid.

The splashy celebrations have also given the party a chance to remind the public of its storied legacy, amid deepening frustration at corruption scandals and unfulfilled promises to the poor.

"Heartiest congratulations on achieving a significant milestone, and I pray that they will be true to where they came from," retired archbishop and anti-apartheid hero Desmond Tutu told the public broadcaster SABC.

The beloved Mr Mandela, who became South Africa's first black president in 1994, is increasingly frail at age 93 and did not attend but his image was present in the stadium awash in ANC colours of green, gold and black as popular musicians took to the stage.

Sunday's events began at midnight with the lighting of a centenary torch, blessed by Tutu in the Wesleyan Church where the ANC was founded on January 8, 1912. The flame will be carried to the rally, where heads of state and foreign supporters are expected.

In his address, Mr Zuma is expected to lay out the party's path forward as he seeks to rein in divisions ahead of year-end party elections where some of his erstwhile backers are now pushing for his removal.

None of those opposed to him, including fiery youth leader Julius Malema who arrived to roaring cheers and song, will be allowed to speak at the rally in what is seen as a show of control of the party.

"Already he has shown that, because there are not any (other) speakers who are going to speak," said youth league member Tefo Labaka, 28, who said other speakers could "pull more ground away from Zuma."

"For now, there is unity because we have to unite for this centenary. But I believe after this event there is going to be a big division," he said.

Mr Malema has styled himself as the voice of South Africa's poor, who increasingly are taking to the streets to demand jobs and better basic services, fuelling divisions within a party that wants to represent billionaires as well as paupers.

Reaching out to the ANC's diverse membership, weekend events included a golf tournament, ritual animal slaughter and concerts.

An interfaith service was held at the Wesleyan Church early Sunday, the morning after African leaders paid tribute to the ANC's inspiration of other liberation movements on the continent.

The party also thanked its international supporters who sheltered its exiles during apartheid and campaigned for the end of white-minority rule.

"No longer in South Africa will you see signs: Europeans only, non-Europeans only, non-Europeans and dogs not allowed. All of South Africa is now free. We have won our dignity as human beings," said party veteran Ahmed Kathrada, who was jailed alongside Mandela.

Founded to fight discrimination, the ANC was banned by South Africa's white apartheid rulers in 1960, and its leaders were jailed four years later.

Nearly three decades later, the crumbling regime released Mr Mandela, who oversaw the peaceful transition that set the path for huge wins in regular polls ever since.

But critics say too many people have been left to make do with shoddy public hospitals and schools, a dangerously high joblessness rate of 25 per cent, violent crime and a grim life in shantytowns.