Johannesburg - Thousands of South African workers are expected to down tools on Wednesday to protest against a jump in electricity prices, threatening to halt platinum and gold mines across four provinces in the country.
In the line of fire would be producers such as Anglo Platinum (Angloplat), the world's top producer of the precious metal, which said that none of its mines had so far been affected.
Simon Tebele, a spokesperson for Angloplat, said he would only know the impact of the strike later on Wednesday.
The world's No. 2 ranked producer Impala Platinum (Implats), said its biggest operation, in Rustenburg, had so far not been hit, and that its smaller Marula mine was partially affected by the protest, but the impact on output was minimal.
"The Rustenburg operation is normal, there is no stay away of note, while the Marula has seen about 60% turnout, obviously this will have a slight impact, but it won't be material," Alice Lourens, group investor relations officer said.
Marula produces about 60 000 ounces of platinum a year.
AngloGold Ashanti, the world's third largest gold producer, said it would know the strike's impact later.
Amelia Soares, a spokesperson at smaller rival Harmony Gold, said the company's mineworkers had vowed to take part in the strike, which would shut four mines and six shafts, but she had yet to verify if they had actually downed tools, and how much output was expected to be lost.
The protest is part of a drive by the Congress of South African Trade Unions (Cosatu) and its allies, which include the National Union of Mineworkers (Num), to pressure the government to limit price increases in Africa's biggest economy.
The strike is being held in Gauteng, the Eastern Cape, North West and Limpopo provinces, to protest against rising electricity prices and possible job cuts after a power crisis engulfed the country this year.
Wednesday's strike is the third in a string of rolling protests this month, that will culminate in a national strike on August 6, when the country's mines along with other business are expected to grind to a halt in a massive worker stay away.
Unions are furious over job losses linked to the electricity crisis that began in January, when a near collapse of the system led to a five day shut down of platinum and gold mines.
The state-owned power utility Eskom has been rationing electricity to mines and other large industrial customers since then, with users threatening to shed jobs owing to lower output.
The government has been blamed for not investing in expanding power generation and unions say their workers should not be made to pay for the government's lack of planning. A 27.5% hike in power tariffs for the current year, as well as fuel and food price hikes, have annoyed unions further.