JOHANNESBURG, South Africa (AP) — Nine miners were injured yesterday when a machete-wielding mob attacked union stewards and security guards opened fire with rubber bullets amid ongoing labour rivalry at an Anglo American Platinum mine, police said.

Competition for members between the longstanding National Union of Mineworkers (NUM) and upstart Association of Mineworkers and Construction Union led to violence and wildcat strikes that killed more than 50 people and closed some mines for weeks last year. Police killed 34 striking miners at a Lonmin platinum mine, shocking the nation with their apartheid-era tactics.

Yesterday, a mob of about 100 people attacked four NUM stewards at an Amplats mine near Rustenburg, said police officer Thulani Ngubane. Some miners accuse the NUM, which is allied to the governing African National Congress party, of becoming elitist, cozying up to business and putting those interests before that of mine workers.

When mine security guards attempted to intervene they were attacked, with four cut by machetes, Ngubane said. The guards then fired rubber bullets.

Ngubane said three of the 13 injured are in critical condition.

Amplats said the mine is validating union membership to establish which union has the most members at that and other mines.

Anglo American, the world’s largest platinum producer, announced its first loss in more than a decade in an annual report earlier this month that outlined plans to shut down one mine and lay off 14,000 workers. The report blamed the strikes, in part, but said the company also wants to reduce a glut of platinum on the world market that is bringing down prices. South Africa is the world’s largest platinum producer.

The government reacted with anger. The mining company currently is in negotiations with government officials and unions over its threatened retrenchment.