"The strike started today at all the seven car manufacturing companies across the country," Mpumzi Matungo, the treasurer of National Union of Metalworkers (NUMSA) told AFP.
The workers are demanding at least a 14 per cent pay increase, but employers have offered eight per cent with effect from July 1.
"That has been rejected, and that is why the workers have gone on strike," he said. It's an indefinite strike."
Workers at BMW started striking last Thursday.
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The sector contributes around six per cent to the country's GDP and accounts for roughly 12 per cent of the country's exports. Last year, South African exported 277,893 cars, including to the European Union market.
Some of the world's leading car makers -- including Toyota, Volkswagen and General Motors - have production plants in South Africa.
Work stoppages are common in South Africa in the middle of the year, when collective wage negotiations traditionally get underway.
Wage talks are also taking place in the volatile mining sector where dozens were killed in labour unrest last year.
Last year, the country registered a meagre 2.5 percent growth, hit by the effects of the post 2008 global financial meltdown and the eurozone recession.