South Africa's police have fired rubber bullets and tear gas to disperse striking farm workers in the wine-producing Western Cape region.
The workers barricaded roads and threw stones at police in De Doorns town, a top grape-producing area, local media reported.
The strikers, who pick and pack fruit, are demanding their daily wage be more than doubled to about $17 (£11).
South Africa has been hit by a series of wildcat strikes since last year.
Talks between trade union and employer representatives to avert a strike on the farms broke down earlier this week.
"We have been met with naked racism and white arrogance," said Nosey Pieterse, the general secretary of the Agricultural Workers Union.
'No money for school clothes'
South Africa's labour relations are fraught with racial tension, more than 18 years after white minority rule ended.
Most farm owners are white while their workers are black.
The region, home to South Africa's multi-billion dollar wine industry and a popular tourist destination, is extremely beautiful, but inequality is jarring.
Last week, the powerful Congress of South African Trade Unions (Cosatu) called for an international boycott of Western Cape agricultural produce, if worker demands were not met.
Police spokesman Lt-Col Andre Traut said about 50 protesters had been arrested in protests across the Western Cape, the South African Press Association (Sapa) reports.
The anti-riot force had been deployed to contain the unrest, he added.
"We are taking action, and arrests are being effected," Lt-Col Traut is quoted as saying.
The protest has forced the closure of the main road from Cape Town to Johannesburg, causing major disruption to traffic, reports the BBC's Mohammed Allie from Cape Town.
The protesters who clashed with police have occupied part of the road which is strewn with rocks and boulders, AFP news agency reports.
Our correspondent says journalists have also been targeted by the protesters.
The car of one reporter was set ablaze, and police had to escort journalists to safety, he says.
Some protesters carried placards in the Afrikaans language which read, "Agri SA [a reference to the body representing employers] you are apartheid farmers", AFP reports.
The workers, many of them seasonally employed to pick and pack fruit, say they cannot survive on a daily wage of about $8, Reuters news agency reports.
"We are struggling. School is starting and we don't have money for school clothes," said Lena Lottering, 35, a mother of three.
Another worker, Aubrey Louw, 47, told Reuters he had worked on the farms since the 1970s when he received 45 rand ($5) a day.
"Now we get 65 rand. What is that? We want 150 rand," he said.
"Farmers would rather employ security guards and buy new cars than pay us."
Our correspondent says that while some farmers exploit workers, others have improved their labour practices dramatically since apartheid ended in 1994.
These farmers pay workers a salary way above the minimum wage, and even provide their children with free schooling, our reporter adds.
The farms were hit by a similar strike last year, when two workers were killed in clashes with police.
Police killed 34 striking workers at the Marikana platinum in South Africa's North West province in August, in the most deadly security force action since white rule ended in 1994.