Meanwhile, a report from the Reuters news agency said that at least 5,000 workers gathered outside South Africa's main government building in Pretoria, while other protests took place across KwaZulu Natal province.
The Congress of South African Trade Unions (COSATU), South Africa's federation of trade unions, has said strike action, starting June 1, is unavoidable if the government does not agree to their demands.
Armoured police vehicles and a large security presence accompanied the demonstrators, after marches last year by security guards and other workers turned into riots.
There were no reports of any violence on Friday.
The government is not keen to give in to COSATU's demands, fearing it will worsen the inflationary pressures caused by recent gasoline and food price hikes.
"We don't want our nurses to leave this country. We need them in South Africa"
Tony Ehrenreich, union official
But South Africa, like many African countries, is also trying to combat shortages of professionals, such as health workers, who are lured to Europe and North America by higher salaries.
"We don't want our nurses to leave this country," said Tony Ehrenreich, a trade union official. "We need them in South Africa."
Rosemarie Jones, a psychiatric nurse with 19 years experience, said her take-home pay was barely enough to keep her two children in school.
"Every year I feel like quitting. The only thing that keeps me going is the patients," she said.
She added that growing numbers of nurses were leaving the badly equipped public hospital where she worked and moving into the private sector or working overseas.
In addition to the pay increase, the unions want employers to increase contributions to medical aid and home owners' allowances.