The Economic Freedom Fighters (EFF), the country's third-largest party, called for a "national shutdown" of walkouts and protests, sparking fears of a repeat of unrest that turned deadly two years ago.
In Pretoria's Church Square, a huge poster made from white fabric, with "Ramaphosa must go" written in red paint, was tied to a fence.
"Clearly this government is failing," said Carl Niehaus, a former official of the ruling ANC who joined the mainly EFF supporters for the rally.
"The damage that the Ramaphosa government is causing is so terrible that we cannot tolerate it any longer. They must go now," he told AFP.
Trade unionist Trevor Shaku was among the protesters calling on the ANC government to go.
"They have proven beyond doubt that they cannot rule this country, that they cannot manage this country," he said.
Authorities said they were on high alert to prevent and fight any acts of criminality and maintain public order. Parliament announced that President Cyril Ramaphosa had authorized the deployment of 3,474 soldiers to assist police.
"We hope that those that will be marching, as long as they will be doing so peacefully, we have no reason to interfere with them," police minister Bheki Cele told reporters in Johannesburg on Monday.
"Police will have to be tough without really being brutal," he said, adding that private security companies were also helping police.
South African security forces said on Monday that 87 people had been arrested in the last 12 hours across the country over public violence ahead of planned protests by the EFF.
The EFF called for a national shutdown to protest crippling power cuts and demand the resignation of President Cyril Ramaphosa.
The party's main constituency are the poor and working class Black South Africans who feel left out of the country's prosperity since the governing African National Congress (ANC) ended white minority rule in 1994.
Parliament said in a statement on Sunday that the South African military would deploy 3,474 troops for a month until April 17 to prevent and combat crime in cooperation with the police.
"Law enforcement officers are on high alert and will continue to prevent and combat any acts of criminality," NatJOINTS said.
This report was sourced from Reuters and Agence France-Presse.