South Africa's largest labour federation, the Congress of South African Trade Unions (Cosatu), and alliance partner the South African Communist Party (SACP) are embarking on a protest to "shut down the country" on Wednesday in what they've called post-apartheid South Africa's largest protest.

It remains to be seen how many of Cosatu's 1.2-million members will take part in the protest calling for President Jacob Zuma's resignation and an end to corruption and state capture. The SACP said it had mobilised 250 000 members.

"This strike is about sending a message to both government and private sector that, as workers and citizens, we are tired of corruption," Cosatu general secretary Bheki Ntshalintshali said at a press briefing on Tuesday.

During the briefing, SACP deputy general secretary Solly Mapaila said: "President Jacob Zuma is an elite predator.

"The elite are those who are around him: The Guptas, and those who are inside our movement."

Several marches are set to take place across the country on Wednesday.

'Busy day'

The protest action was approved by the National Economic Development and Labour Council in August.

In Johannesburg, the march is scheduled to start outside the trade union's Braamfontein headquarters at 10:00, moving on toward Johannesburg Mayor Herman Mashaba's office, banks in the city centre and Premier David Makhura's office before ending at the Chamber of Mines.

Johannesburg metro police spokesperson Edna Mamonyane said it was going to be "a busy day in the city centre".

On Monday, Mashaba dismissed the march to his office and said it "fails to take the protest to the headquarters of State capture, Saxonwold, at the Gupta residence".

In Cape Town, an estimated 10 000 marchers are set to make their way past Western Cape Premier Helen Zille's office and Parliament.

Cosatu Western Cape is calling on both Zuma and Zille to resign.

Activist Zackie Achmat said he would be joining the marchers. He said South Africans had to unite in "times of crisis".

"Regrettably, the unions led by comrade Zwelinzima Vavi and Saftu have failed to grasp this moment to help to further break the hold of the bankrupt ANC on significant sections of the working class," he said in a Facebook post on Tuesday.

On Tuesday evening, Lieutenant-General Elias Mawela, the acting chair of the National Joint Operational and Intelligence Structure, warned those who plan to take part in the mass protest action to respect the country's laws.

"It is in the best interests of all parties to work together to avoid unnecessary conflict situations. People who do not follow the correct procedures and the rule of law will be held accountable," Mawela said in the statement.