JOHANNESBURG (Reuters) - South African Coal Mining Holdings said on Wednesday operations at its Umlabu colliery have been interrupted due to a strike, signaling spreading labor unrest in the domestic mining sector that has choked output.
About 100,000 workers in South Africa have downed tools for better pay since August in a wave of strikes that has sparked two credit downgrades.
SA Coal Mining, a junior coal producer, said the strike by the National Union of Mineworkers is over a wage dispute.
Several companies have issued ultimatums to wildcat miners to return to work or face dismissal as South Africa struggles to resolve the unrest that has poisoned labor relations, marred its image overseas and is spreading beyond the mining industry.
Striking miners at AngloGold Ashanti, the world's No.3 gold producer, have until midday to return to work or be fired. The company said on Tuesday it was seeing positive signs that workers will return to work by the deadline.
The bulk of workers at AngloGold's two mines, Kopanang and Great Noligwa, had returned to work.
Rival bullion producer Harmony Gold has also given wildcat strikers an ultimatum to return to work on Thursday.
The hardball tactic has not always worked. Gold Fields, the world's fourth-largest bullion producer, sacked 8,500 wildcat strikers at its KDC East mine on Tuesday after they ignored an ultimatum to return to work.
Anglo American Platinum (Amplats), the world's largest platinum producer, was the first to take a stand against wildcat strikes, sacking 12,000 workers at its Rustenburg operations earlier this month.
Last week it said it would delay the dismissal process at its Union and Amandelbult operations, where it employs 20,500 people. It also said it was open to discussing the reinstatement of the sacked workers with unions.
The strikes spread to other mining industries after starting in the platinum mines.
(Reporting by Olivia Kumwenda; editing by David Dolan)