In a statement, Anglo said an incident had occurred between members of the workers committee and National Union of Mineworkers stewards yesterday.
The mine, located in the Rustenburg area, was the centre of unrest last year when Anglo was forced to shut down operations, citing the safety of its employees from the intimidation of protesting mine workers outside.
The company said workers committee members were contesting NUM’s legitimacy at the mine and demanding that NUM vacate its offices.
The ABC quoted the local police saying up to 100 people were involved in the attack in which machetes were reportedly involved.
Nine employees first became injured after rubber bullets were fired by Anglo American Platinum security personnel.
However, the number increased to 12 when three security personnel sustained minor injuries after attempting to evacuate the NUM shop stewards who were trapped in their offices.
All of the injured employees received medical attention for non-life threatening injuries, with no fatalities reported.
“The company is currently in the process of validating union membership at Rustenburg and the mines north of the Pilanesberg,” Anglo said.
“Anglo American Platinum expresses its deep concern about this incident and appeals for its employees to remain calm and respect the company’s dispute resolution process.”
Not many companies were immune from the spate of industrial unrest at South Africa’s mines last year.
At the height of the disorder, violence between striking miners and police at Lonmin’s Marikana platinum mine in the country’s northwest province led to the deaths of about 44 people while more than 70 were injured.
AngloGold Ashanti was another major impacted by the widespread unrest, with strike action taking place at six of its mines last September.
Anglo American was hit hard by the strike action, which impacted on platinum and iron ore output.
The ongoing illegal strike action, in addition to increased costs, forced Amplats earlier this year to announce a sweeping restructure of its business, with changes expected to deliver about $A41.9 million in savings.
Outgoing Anglo American chief Cynthia Carroll told delegates at this month’s Investing in African Mining Indaba in Cape Town that no one benefited from anarchy in the workplace.
“Violence and criminality are always unacceptable and they must never be tolerated by society,” she said.
“It is in the interests of all stakeholders – employers, employees and trade unions – for there to be orderly and fair processes to regulate union recognition and collective bargaining.”
Anglo recently booked a $US239 million ($A230 million) loss for 2012 as a result of a $4.6 billion impairment charge relating to cost blow-outs at its Minas-Rio project, weak commodity prices and increased cost pressures.