Members of COSATU accuse Jacob Zuma of massive looting of state resources and collusion with the influential Gupta business family.
Thousands of angry South African trade unionists took to the streets across the nation on Wednesday to call for President Jacob Zuma to resign over alleged top-level corruption.
In Johannesburg roughly 2,000 members of the COSATU (Congress of South Africa Trade Unions), South Africa's largest, marched armed with "Zuma must go, corruption is a crime against humanity" placards.
They accuse Zuma of massive looting of state resources and collusion with the influential Gupta business family which is at the centre of many of the graft allegations against the president.
COSATU, which along with the South African Communist Party (SACP) and Zuma's African National Congress (ANC) party, is in South Africa's ruling coalition but has previously broken ranks and called for the president to go.
COSATU backs Deputy President Cyril Ramaphosa, a former trade union leader and businessman, in the race to replace Zuma as party leader which will conclude at the ANC's elective conference this December.
Zuma, who denies all allegations of corruption, must also step aside as South Africa's president in 2019 when the ANC leader will likely succeed him as head of state.
Ramaphosa: 'man of good morals'
But COSATU's president Sdumo Dlamini, who led marchers in Durban, denied the protests were intended to sway December's conference and insisted they were simply to protest graft.
"(The) ANC needs to prioritise unity so that we can see a united outcome of their conference in December," he told local media.
In Johannesburg, a sea of red-clad demonstrators nonetheless chanted: "We are ready for Ramaphosa."
"The president of the country must step down because of his dubious relationship with the Guptas," said 48-year-old Lucas Makgolane, a high school teacher who traveled to the city from Heidelberg, some 60 km (40 miles) to the southeast.
"If Zuma steps down then the deputy president, a man of good morals, can step in."
Smaller marches were also held in Cape Town and in several of South Africa's major towns.
Not just Zuma
Zuma has shrugged off several court cases and persistent allegations of graft and incompetence.
Criticism of his leadership is growing within the ANC and several marchers wearing the party's colours took part in Wednesday's action.
As South Africa's economy struggles to rebound following years of sluggish growth, some political analysts have suggested the ANC could lose its absolute majority in parliament, held since the dawn of democracy in 1994, in 2019's elections.
Not everyone at the march wanted to see Zuma ousted, however.
"It's not right that this march has turned into a factional platform," said Bongo Dlamini, a 24-year-old school teacher wearing a neatly-tied ANC headscarf.
"Zuma must stay because there are a lot of other members (of the ANC) who have done similar things."