Image caption Fears over a repeat of last year's protracted strike have hit shares in Lonmin

Workers at Lonmin's platinum operations in South Africa have gone on a wildcat strike.

The action follows the shooting of a union official at the weekend and has reignited fears of the violence that hit the industry last year.

Last August, 34 miners were shot dead at Lonmin's Marikana platinum mine near Rustenburg.

Lonmin, whose shares are listed in London and Johannesburg, is the world third-biggest platinum producer.

News of the strike sent shares in Lonmin down 5% in London during morning trade.

Lonmin spokesperson Sue Vey said that all of the company's 13 shafts were "not operational".

"Employees arrived at work but did not proceed underground," she added.

While she said the company had no indication yet as to why the strike was taking place, a spokesman for the National Union of Mineworkers (NUM) said the strike appeared to stem from anger over the killing at the weekend of an organiser from the rival Association of Mineworkers and Construction Union (AMCU).

Police confirmed that a 46-year man who was "alleged to be the regional organiser of AMCU", had been killed in a tavern near Rustenburg on Saturday night.

The platinum belt has been a been at the centre of tensions between the NUM and AMCU. Last year, tens of thousands of workers switched their allegiance to AMCU.

AMCU was recently recognised as the majority union at Lonmin and at neighbouring Anglo American Platinum (Amplats), dislodging the powerful NUM from the top position.