Thousands of South African farm workers will go on strike in the Western Cape wine region from Wednesday, reviving labour action for higher wages in which two workers were killed in clashes with police and vineyards were damaged.

Africa's largest economy was crippled by waves of violent strikes last year that started in the platinum industry and spread to truckers and farm workers.

The farm workers, many of them black seasonal hires employed to pick and pack fruit, suspended their strikes in December after vineyards and warehouses were set on fire and at least two workers died in clashes with police.

"We have not reached a deal because of the intransigence of farmers," said Bawsi Agricultural Workers Union of South Africa general secretary and union leader Nosey Pieterse.

"We have been met with naked racism and white arrogance."

Almost two decades after the end of apartheid, the commercial farms are still largely white owned, with accusations of racism and mistreatment of workers commonplace.

Workers, who want their minimum daily wage of R69 increased to R150, have been negotiating directly with farm owners on an individual farm-by-farm basis since December's action was called off.

But farmers, who are already battling rising electricity and fuel costs, say the demands are too high.

"There is no farm in South Africa that can afford R150," said industry body Agri-Western Cape representative Carl Opperman.

Harvest Season

Farm workers are among the lowest paid in the country and often live in squalid conditions with no hot water or electricity – yet their labour at this harvest time is vital for producing wine that is increasingly popular around the world.

Unions are urging an international boycott of South African agricultural products because they are "produced under slave conditions", said labour federation Cosatu representative Tony Ehrenreich.

South Africa's global reputation was tarnished last year in the wave of violent strikes, when police shot dead 34 striking miners in a single day – the bloodiest security incident since the end of apartheid in 1994.

The government warned against further labour violence.

"The government will not tolerate violent labour disputes and calls on all parties to always strive to reach a common ground," State spokesperson Phumla Williams said in a statement.

The government sets a three-year minimum wage for the agricultural industry and is expected to announce a new minimum early in April.

According to statistics from the South African wine industry, the country is forecast to export a total of 440.2-million l of wine in 2016 from 379-million l in 2012.

It contributed 2.2% to gross domestic product in 2008, with exports rising by 18.3% over the year from December 2011 to November 2012.