The action, which will test the African National Congress government's relationship with its large trade-union support base, involves more than 500,000 workers.
It is the biggest strike since the ANC came to power in 1994 and follows union action linked to fears of job cuts in the mining sector as a result of the falling gold price.
But in Soweto some workers at the Chris Hani-Baragwanath Hospital felt that to strike amounted to betraying the government they had struggled for in the apartheid years.
On a small but vociferous picket line outside the 3,000-bed hospital, Lindelwa Dunjwa, a nurse in the 230,000-strong National Education, Health and Allied Workers Union (Nehawu), said: "We need to convince the workers that we are not fighting against our government. We are fighting against the employer.
"In the struggle against apartheid we were fighting for workers' rights and we must flex our muscle.''
A spokeswoman for the hospital said most of the 7,000 staff had turned up for work. "There is a good relationship between unions and the administration, because everyone here does an important job for Soweto,'' said the spokeswoman, Hester Vorster, who was helping out in the maternity ward.
But Jabu Buthelezi, a porter and Nehawu member, said that even though he had been among those who last month handed the ANC a two-thirds majority in the country's second democratic elections, he could not live on 1,900 rand (pounds 200) a month. "My wife is a nurse, we have three children, and we take home around 3,000 rand between us.
"We are living in a debt trap. Some months we have to go to the loan sharks just to get enough money to pay our transport to work.''
The president of Nehawu, Vusi Nhlapho, turned up at the singing and dancing lunchtime picket to show his support. "This is only the first day of the strike. It will expand next week if the government does not make an improved offer,'' he said.
But the Public Service Minister, Geraldine Fraser-Moleketi, said only that she hoped the parties would "arrive at a formula within the present fiscal constraints".
The government has said it has only R3.2bn to fund the public-sector pay increase - equivalent to a 6.3 per cent pay rise for the majority of the public service and 6.8 per cent for teachers.
Ms Fraser-Moleketi said that even though the industrial action is legal, strikers will not be paid. "We are going to effect the no-work, no-pay rule, because we are aware that if you are engaging in strike action it is very clear that you are willing to consider a sacrifice," she told national radio.
There were reports that teachers, 80 per cent of whom belong to the South African Democratic Teachers' Union, had supported the strike in large numbers. Police unions were spreading their strike over several days.
Most government offices were closed yesterday. The public-sector strike comes 10 days after some 6,000 mineworkers marched on the British High Commission and the Swiss Embassy in Pretoria to demand an end to gold sales by central banks and the International Monetary Fund.
The financial markets' reaction to planned gold sales - to fund Third World debt relief and as part of central banks' moves to reduce their reserves of the metal - has caused a slump in the industry.
Two gold mines are on strike over retrenchment plans for more than 1,000 workers and there are predictions that the industry will cut up to 28,000 jobs in the next three months.