Tens of thousands of South African public servants marched to government offices in Pretoria and parliament in Cape Town during nationwide marches.
The main union federation, Cosatu, has called on more than 1m workers to strike over a wage dispute.
Cosatu has threatened a "full-blown strike" if their demands are not met.
By law, essential workers such as doctors and police officers are not allowed to strike, but many schools around the country are closed.
South Africa has been hit by a wave of strikes in recent years.
During the World Cup, hosted by South Africa in June and July, transport and power supply worker unions won pay rises after threatening to strike during the tournament.
The BBC's Karen Allen in the capital, Pretoria, says workers, including nurses, teachers and prison officers, marched through the streets peacefully.
Last week, government employees rejected a 7% pay offer.
Instead they want the government to boost it to 8.6%, which is nearly double the rate of inflation, our reporter says.
A petition demanding wage increases was handed to Public Service Minister Richard Baloyi in Pretoria
"As teachers, we are hungry and angry," John Molebedi, a high school teacher on the march, told AFP news agency.
"We need money. A teacher can't even afford a house," he said.
As people were gathering for the Pretoria march, Cosatu spokesman Patrick Craven said union members were open to new offers to suspend the strike.
"We believe money is available. There have been stories recently of the government spending huge amounts of money on World Cup tickets for their senior managers, on five-star accommodation for government ministers," he told the BBC's Network Africa programme.
"We simply do not accept that, given the importance of paying public servants a decent wage, money cannot be found from the huge amounts the government has at its disposal."
Around 30,000 civil servants also marched to parliament in Cape Town, where Zwelinzima Vavi, Cosatu's general secretary, took issue with President Jacob Zuma's salary.
"I asked the president a while ago what he is earning," he told the crowd.
"If my memory serves me right he is earning more than 2.2m rand [about $300,000, £190,000]," he said to a roar of disapproval, the South African Press Association reports.
The average annual salary for a teacher in South Africa is about $15,000.
Three years ago, hundreds of thousands of public workers staged a month-long strike which led to the closure of schools and military personnel being brought in to help in hospitals.
This was before President Zuma came to power, but analysts say the government is keen to avoid a repeat of that stoppage.
Mr Zuma, who owes his political support to South Africa's powerful trade unions, has little room for manoeuvre, our correspondent says.
He is under pressure to appease the unions while at the same time address the country's budget deficit and deliver on a promise to create more jobs.