Hundreds of people barricaded roads leading to a mine of the world's top platinum producer Anglo American as labour unrest spread in South Africa's key industry, police said.
"There is a strike, mine workers are gathering," police spokesman Thulani Ngubane told AFP.
"They are rioting, barricading the roads with tyres, trees trunks and rocks."
He said four shafts were affected by the unrest, adding "the situation is under control."
Anglo American Platinum (Amplats) denied its workers were on strike, instead saying there is widespread intimidation of its employees.
"Mine employees are not on strike. We are aware of widespread cases of intimidation which have been reported throughout the Rustenburg area," Mpumi Sithole, spokesman for the mining giant said in a statement.
He said some Amplats workers "were unable to clock in for night shift due to fear of intimidation and threats by unidentified individuals in and around our Rustenburg operations."
Media reports say some 15,000 Amplats workers have embarked on a strike, but their demands were not immediately clear.
South Africa's mines have in recent weeks been hit by unrest following a wildcat strike at Lonmin's Marikana platinum mine that has so far claimed 45 lives.
On Tuesday the country's maverick politician Julius Malema called for national strikes across all South African mines for five days each month, to fight for a basic salary of 12,500 rands ($1,533), around three times the current average.
Malema was addressing thousands of workers at a stadium in the gold mining town of Carletonville where around 15,000 gold miners have been on strike since Sunday night.
The Lonmin mine is part of the same platinum belt as the Amplats site, northwest of Johannesburg.