According to the Warsaw Business Journal, a general coal miners’ strike was planned to start on February 2.

It has been separately referred to as a “sympathy strike” to the workers who went on strike against Polish state-owned miner Jastrzebska Spolka Weglowa last week.

That industrial action, based on plans to remove social benefits and dismiss union leaders according to a union campaign, was already threatening the Polish division of leading steelmaker ArcelorMittal with a coking coal shortage.

"The situation is tough, as JSW provides up to 60 percent of the coal we use," an ArcelorMittal Polska spokeswoman told Reuters on Friday.

"In the medium and long term we can cope, but as we have a few days' worth of resources, in the coming days we may have to curb production. We're trying to look for alternative supply sources. A ship with overseas coal is on its way."

Last month unions resisted Polish government plans to close four loss-making coal mines owned by state-run Kompania Weglowa.