UNLISTED coal producer Shanduka Coal has dismissed about 250 mineworkers for taking part in a week-long unprotected strike followed by violent clashes at its Graspan colliery in Mpumalanga.

Graspan supplies thermal coal for both the domestic and international markets.

On March 18, the employees broke ranks from formal bargaining structures and downed tools, demanding performance bonuses, as unprotected industrial action in the coal mining sector intensified.

Their demand for bonuses was despite not having achieved production targets for February, the company said.

"The situation at Graspan colliery is calm and returning to normal," chief operating officer Zirk van der Bank said on Tuesday. "The illegal strike action was isolated and occurred only at the Graspan colliery."

The dismissed employees would be able to appeal against their dismissal and the company would recruit new employees from surrounding communities, Mr van der Bank said.

The announcement comes a couple of days after mineworkers at six coal operations owned by Exxaro Resources agreed to return to work after reaching a settlement with the JSE-listed diversified resources miner.

Exxaro is one of Eskom’s major coal suppliers, and the three-week unprotected strike action at its Arnot, Matla and Grootegeluk mines had raised concern about the impact on supplies for Eskom’s power stations.