JOHANNESBURG: At least 13 workers were injured at an Anglo American Platinum mine in South Africa on Monday, some shot with rubber bullets and others hacked with machetes, in the year's first major mine violence after the sector was plagued by deadly strife in 2012.

Police said the bloodshed was provoked by a dispute between the established National Union of Mineworkers (NUM) and the growing Association for Mineworkers and Construction Union (AMCU) over access to mine offices.

The membership turf war between rival unions has rocked the country, which has the world's largest known reserves of platinum. It has dented investor confidence and slowed growth as production has fallen.

Police said it was unclear who started the violence at the mine in the Rustenburg region, about 120 km (70 miles) northwest of Johannesburg. But the mine's security guards used rubber bullets to disperse rival union members who had gathered near a union office at a shift change.

"There are 13 people who have been admitted at Bleskop hospital. There are no fatalities at this stage," police spokesman Thulani Ngubane told Reuters.

Anglo American Platinum, or Amplats, the world's largest platinum producer, said: "A total of nine employees were injured when rubber bullets were fired by Anglo American Platinum security personnel."

"No one was fatally injured during this incident," it said in a statement.

"AMCU members were intimidating NUM officials at the office," NUM spokesman Lesiba Seshoka told Reuters.

AMCU treasurer Jimmy Gama told Reuters: "We can confirm the incident but at this stage we cannot say what led to it. We are still getting more details."

More than 50 people were killed in labour strife last year, including 34 shot dead by police at Lonmin's Marikana mine in August - the deadliest single security incident in South Africa since apartheid ended in 1994.

Anglo American Platinum angered workers and the government in January when it said it planned to mothball two South African mines, sell another and cut 14,000 jobs.

Amplats, the world's largest platinum producer, was hit by violent strikes last year, caused in large part by the union battle for membership.

South Africa's ruling African National Congress has tried to reassure investors the strife is not undermining Africa's largest economy, which had its sovereign credit rating downgraded by Fitch last month due in part to the labour problems.

Amplats shares closed down nearly 5 percent on Monday in trading in Johannesburg.