Johannesburg: South African council workers crippled public services for the fourth day on Thursday after refusing to accept a pay offer, in a sign of further defiance among President Jacob Zuma's union backers.

The SAMWU municipal workers' union said it would hold more talks with local government bosses, who are refusing to bow to worker demands for a 15 per cent salary hike - more than double the 6.9 per cent annual inflation rate.

"We discussed a number of ways of resolving the impasse and we will approach the negotiations set for Friday with a view to reaching an agreement that meets the needs of our members," the union, which represents 150,000 workers, said.

Pressure on Zuma, who won a presidential election in April with strong union and leftist backing, eased on Tuesday when the country's biggest union agreed a pay deal with gold and coal producers.

Paper, chemicals, pharmaceutical and petroleum workers also called off strikes this week after agreeing wage deals, but a 60,000-strong clothing union declared a national pay dispute on Thursday threatening a strike.

Some council workers have resorted to trashing city centres to make their voices heard and police have fired rubber bullets to disperse crowds of unruly marchers.

SAMWU accused the authorities of being antagonistic and heavy-handed.

The sporadic unrest followed days of violent protests by impoverished township residents complaining about a lack of healthcare, water and electricity 15 years after the fall of apartheid.

The cabinet condemned the "violence, destruction to property, vandalism and intimidation of innocent citizens" in a statement echoing Zuma's call on Wednesday for police to arrest troublemakers.