South Africa's army has been called in to protect hospitals from striking public sector workers.
More than a million civil servants began an indefinite strike on Wednesday, calling for higher wages.
Earlier, police fired rubber bullets and water cannon at crowds of strikers protesting outside a Soweto hospital.
Military doctors, nurses and soldiers have been deployed to three out of South Africa's nine provinces.
More unions joined in on the second day of industrial action.
Gauteng province's health minister said they were investigating whether the deaths overnight of five people in a hospital east of Johannesburg were linked to staff shortages because of the strike.
Unions affiliated with Cosatu, South Africa's main union federation, have been holding out for an 8.6% pay rise.
But South Africa's government says it can barely afford the 7% offer it has put on the table for the police, teachers, doctors and nurses.
President Jacob Zuma has condemned the union's threat of violence against non-striking workers and said the government reserved the right to fire the strikers.