Machete-wielding strikers forced top world platinum producer Anglo American Platinum to shut down some of its South African operations on Wednesday.
A column of 1,500 chanting marchers confronted a small group of riot police backed by armoured vehicles on approach roads to the firm's Bathopele shaft in the "platinum belt" near Rustenburg, 100 km northwest of Johannesburg.
The protesters jeered workers inside the plant, a repeat of action taken on Monday at rival Lonmin's neighbouring Marikana mine, where police shot dead 34 protesters on August 16.
"All of us, we're going to close all the operations, starting from Rustenburg. We'll go even to the gold mines to stop the operations," marcher Evans Ramokga said.
The platinum price jumped 3 per cent to $1,654.49 an ounce, its highest since early April, during the day due to investors' fears of more disruption to supplies of the precious metal used in jewellery and vehicle catalytic converters.
South Africa is home to 80 per cent of known reserves of platinum, the price of which has gained nearly 20 per cent since the Marikana shootings, the bloodiest security incident since the end of apartheid in 1994.
The rand also dropped two per cent.
The "Marikana massacre" has poisoned industrial relations across the mining sector and highlighted the ruling African National Congress's failure to keep its promises to reduce poverty in the post-apartheid era.
The bloodshed and the government's inability to resolve the unrest undermining already shaky growth in Africa's biggest economy is also fuelling a campaign against President Jacob Zuma, who faces an internal ANC leadership battle in December.
Anglo American Platinum, also known as Amplats, said it had halted work at its four Rustenburg mines, which account for 17 per cent of its output, due to fears for the safety of its 19,000 staff there.
Police said the trouble started with a confrontation between 1,000 demonstrators and mine security on Tuesday night, before spreading to other shafts owned by the company, which accounts for 40 per cent of world platinum output.
Amplats's Rustenburg shafts have been under pressure since platinum prices collapsed after the 2008 financial crisis. Analysts expect them to be targeted as "restructuring candidates" by parent company Anglo American.
The strikes, which stem from a challenge by the small but militant Association of Mineworkers and Construction Union (AMCU) to the dominance of the ANC-affiliated National Union of Mineworkers (NUM), are also spreading into the gold sector.
The NUM said workers at the Beatrix mine, run by world No. 4 producer Gold Fields, were set to strike this week, compounding wildcat industrial action by 15,000 workers underway at the company's KDC West mine west of Johannesburg.
ANC renegade Julius Malema - the de facto face of an unofficial "Anybody but Zuma" rebellion in the ANC - called on Tuesday for a national mining strike, and repeated this on Wednesday.
"We are calling for mine change in South Africa. We want the mines nationalised. We want the workers paid a living wage," Malema said on Talk Radio 702.
Ministers and NUM leaders have dismissed Malema as an irresponsible opportunist but the expelled ANC Youth League leader is becoming a star among the legions of poor whose lives have changed little in the 18 years since apartheid ended.
Malema has tapped into workers' discontent with NUM and ANC leaders who are accused of getting rich and cozying up to mine companies while ignoring the harsh living conditions of many of South Africa's black majority.
"All they know is to put the money in their pockets," said another Amplats protester, who called himself Mr. Anonymous.
Shares in Amplats, which had largely avoided the labour unrest this year that has hammered rivals Impala Platinum and Lonmin, fell 4.6 per cent.
Anglo American, which owns 80 per cent of Amplats, shed 3 per cent in early trade although later recouped most of those losses.