“The tremor occurred at 11:44am when 12 miners were working 900 metres underground on a crosscut extension,”Xinhua reported.

“Two Czechs and one Pole died at the site. The injured miners have been sent to nearest hospitals.”

OKD spokesman Marek Sibrt said the tremor struck while the 12 workers were doing maintenance work.

“Of course, we do our utmost to prevent tremors, by preventive blasts, for example, but sometimes nature is stronger than us," Sibrt reportedly said.