Wage negotiations between workers in South Africa's coal sector and the employers' body, the Chamber of Mines, reached deadlock on Wednesday and will now go to mediation.

"The employer came back with nothing after we rejected their offer. We have declared a dispute and will go through a mediation process," Peter Bailey, the coordinator for National Union of Mineworkers told Reuters.

Workers want pay increases of up to 15 percent, while the chamber - which represents firms such as Glencore, Anglo American Coal and Exxaro - had offered a revised wage rise from its initial offer of between 4 and 6.5 percent.