JOHANNESBURG (Reuters) – Glencore has laid arson charges against a South African mining union as a three-week coal strike turns increasingly violent, the mining company said on Thursday.

Workers from the Association of Mineworkers and Construction Union (AMCU) torched two trucks and offices at the Wonderfontein Mine on Wednesday night, taking the petrol bomb incidents to around 10 since the strike started, Glencore said.

Around 60 striking workers accused of intimidating other employees and damaging nearby farms have been arrested.

AMCU and the police were not available to comment.

Wonderfontein is a joint venture between Glencore and Shanduka Group, which was founded by Deputy President Cyril Ramaphosa. The mine produces 3.6 million tonnes annually.

Glencore said it was engaging with AMCU leadership over a wage dispute.

(Reporting by Zandi Shabalala; Editing by Joe Brock)