South African police said 13 people were wounded in gunfire and machete attacks at an Anglo American Platinum mine on Monday, after security guards battled to disperse a 1,000-strong mob that besieged a rival union's office.
The skirmishes broke out in the tinderbox northwest platinum belt, where labour violence killed more than 50 people last year.
The violence at the mine was sparked by the return of four shop stewards from the National Union of Mineworkers.
A large mob which gathered around the office is thought to be linked to the Association of Mineworkers and Construction Union.
"Mine security intervened and fired rubber bullets, and in the process a total of 13 mine workers inclusive of four security guards (were injured)," police spokesman Thulani Ngubane said.
"Some of the people were hacked with pangas (machetes) and sharp objects, while others were shot with security rubber bullets."
Strike-scarred Amplats, the world's top platinum producer, confirmed the clashes at its Siphumelele mine saying the wounds were not life threatening.
"Workers committee members are contesting NUM's legitimacy at the mine and demanding that NUM vacate its offices," said Amplats in a statement.
NUM spokesman Lesiba Seshoka described the attack as "unacceptable."
"We are not going to close, we are not going to go underground. We remain the majority union there."
The news saw Amplats share price plunge five percent on trading at the Johannesburg Stock Exchange and the rand weaken.
The battle for control of workers was partly blamed for the outburst of last year's deadly wildcat strikes that rattled the country's vital mining sector.
Amplats on January 15 announced plans to slash some 14,000 jobs but the layoff procedures have been put on hold for the talks following an outcry from unions and the government over the global miner's restructuring move.
Emerging market analyst Peter Nomura said the latest clashes are just a reminder that South Africa's mining woes are far from over.
"Protest action has been rumbling on for some time and the mine there has never really recovered since being at the heart of the action... last year even though most workers did return to work," said Nomura.
Amplats appealed for calm in the wake of the clashes, as analysts warned that further deaths of union members is the last thing Amplats need.
President Jacob Zuma on Thursday said mining royalties will be reviewed.
It was the first clear indication that royalties are up for review in the mining sector -- the bedrock on which Africa's wealthiest economy was built.
Operations at the world's number one platinum producer were crippled by rolling strikes over wages that hit the country's mining sector last year.
The dispute halted mining at some Amplats mines for months, forcing a slump in fourth quarter production.