South African police on Monday fired rubber bullets and teargas at stone-throwing grape pickers in a wine producing town southwest of the country.

Dozens of striking farm labourers pelted officers and journalists on the streets of Villiersdorp, a town which lies on a popular wine tasting belt.

Earlier police had used a stun grenade to disperse a pre-dawn protest in the nearby flashpoint town of De Doorns, as the labour unrest resumed after a weekend hiatus.

Police officers had come under attack during street patrols in the town, which is a major fruit-growing region and the epicentre of violent strikes for better wages.

The N1 main freeway linking the Cape region and the commercial hub of Johannesburg remained closed for a sixth straight day on Monday due to the protests which threaten the harvest of one of South Africa's leading exports.

Police forces stepped up their presence in De Doorns, deploying at least six armoured vehicles after the early morning attack on their colleagues.

"At approximately 3.00 am (0100 GMT) police members on foot patrol in the informal area of De Doorns were attacked by a group of people," said November Filander, police spokesman for the region.

Police used "a stun grenade to disperse the group," he told AFP. Three people were arrested for public violence.

Unions at the weekend vowed to intensify violent stoppages in the picturesque Western Cape wine lands to push for a wage hike from 69 rand (RM23) to 150 rand (RM50) a day.

Many of those on strike are seasonal workers, according to farmers.

Police last week used rubber bullets as they fought running battles with the thousands of strikers in the strife-hit areas. At least 125 arrests were made in three days of clashes.

The Bawsi Agricultural Workers' Union of South Africa (Bawusa) general secretary Nosey Pieter said the strikes would continue as the farmers had not come up with a tangible offer at talks held on Friday.

"The resounding message is that the strike will continue," he said.

He alleged that the main farmers union Agri SA was trying to "sabotage" wage talks launched by individual farmers and unions, saying: "This is the hypocrisy of some of the partners."

Government mediators at the weekend offered to facilitate talks.