Patrick Craven, the Cosatu spokesman, said: "Reports so far indicate a very, very good turnout."
Cosatu, which represents about 60 per cent of the nation's nearly one million public servants, had aimed to shut down most public services in a wage dispute with the government.
Workers' anger was stoked recently by an official body's recommendation that Thabo Mbeki, the president, receive a 57 per cent pay rise.
Unions have demanded a 12 per cent increase, while the government has proposed six per cent.
"Fifty-seven per cent for fat cats and six per cent for poor hard workers. Shame on you," one placard brandished by a picketer at a Johannesburg hospital said.
The government, seeking to keep a lid on inflation, boosted its offer on Wednesday to a 6.5 per cent to nine per cent increase, but talks have been acrimonious.
The government issued a statement reminding essential workers such as firemen, police officers and doctors that they were barred from striking and a court order banned immigration officers from joining the action.
But hospitals appeared particularly hard hit by the strike, with nurses and cleaners picketing in Johannesburg and Cape Town over salary levels which see some nurses earning $640 a month.
Danny Losaba, the union shop steward at Johannesburg General, said: "Today is the beginning of the strike. Until they reach an agreement, the hospital is going to run on half-staff."