JOHANNESBURG (Reuters) - At least 13 workers were wounded by rubber bullets or machetes in fighting at a mine in South Africa on Monday in the first major mine violence this year after deadly strife in the sector in 2012.

Police said the bloodshed at the Anglo American Platinum mine 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 a mine office.

The membership turf war between the 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 the violence started when four likely NUM workers on special leave tried to occupy the union office at the mine in the Rustenburg region, about 120 km (70 miles) northwest of Johannesburg. About 1,000 suspected AMCU workers gathered to force them out.

“The alleged NUM members survived by running for their lives,” police spokesman Thulani Ngubane said in a statement.

The mine’s security guards used rubber bullets to disperse the rival union members. The 13 have been admitted to hospital and there were no fatalities, police said.

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.”

TROUBLED MINES

More than 50 people were killed in labor 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.

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 labor problems.

Amplats this month reported its first-ever annual loss, battered by six weeks of violent strikes last year, soaring costs and flagging platinum prices.

The company, which is 80 percent owned by mining giant Anglo American, has announced a drastic cost-cutting plan that risks sparking more labor unrest.

Amplats plans to cut 14,000 jobs, mothball two South African mines and sell another to right its ailing business.

While a turnaround at Amplats is critical for the fortunes of its underperforming parent, unions have promised to fight any cutbacks.

Amplats is the third worst-performing stock on Johannesburg’s benchmark Top-40 index over the last 12 months, down nearly 21 percent.

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