LONMIN, the world's third-largest platinum miner, said production at its Karee mine at its Marikana operations were disrupted by an unprotected strike.

Production has been disrupted since the Tuesday night shift at Karee, which is the biggest underground mine at Marikana, producing 1,1 million tons of the 2,7 million tons in the March quarter.

It appears the strike does not have the backing of the National Union of Mineworkers (NUM) and a dispute between the regional union leadership and the union leadership on the mine lies at the heart of the industrial action.

"Lonmin management has been informed by the NUM Rustenburg regional office that they have suspended the leadership of the NUM Karee branch, a decision which the NUM Karee branch leadership is disputing and which has resulted in this industrial action," Lonmin said.

"The NUM Regional office representatives are attempting to resolve the matter. The employees have been notified in writing that their activity is unprotected," it said.