Six people, most rescuers, were killed in an explosion in a mine where 26 miners were trapped three days ago, foreign media reported.
Rescuers have entered the Severnaya mine in a bid to save the trapped miners but was killed in the explosion.
But, now all 26 miners are presumed dead, officials said.
"Six people died, five of them rescuers," Anton Kovalishin, a spokesman for the emergencies ministry in the Komi region where the Severnaya mine is located, told the AFP news agency.
On Thursday four miners were killed and 26 were trapped after the Severnaya mine collapsed.