Five major unions of mine workers at state-run Coal India (CIL) have begun what they have indicated could be their biggest strike ever.  The strike began on Tuesday, to protest a government plan to allow private entities to mine and sell coal.

Coal meets more than 50% of India’s energy needs, and mines run by CIL feed all but four of the 86 thermal plants.

“This will probably be the biggest ever strike in the industry. The power sector may be hit by the prolonged strike,” Gurudas Dasgupta, general secretary of the All India Trade Union Congress (Aituc), said – Aituc is one of the five unions that called the five-day strike.

The walkout began with the first shift Tuesday and is scheduled to end with the third shift on January 10, Dasgupta said.

CIL has more than 500 000 permanent and contractual employees.

The government recently renewed  an ordnance for the re-allocation and e-auction of 204 coal blocks, after the Supreme Court cancelled a 2004 allocation that it said did not follow legal procedures. These auctions would be open to private bidders.

India is the world’s third-largest coal producer, after China and the United States.