Footage from the scene showed thick plumes of grey smoke erupting from the mine shaft.
The blaze has been contained but not put out completely, the authorities said some 7 hours after the fire ripped through the mine.
The incident occurred at 12pm local time, according to the mine’s owner, the Uralkali fertilizer producing company. The blaze erupted during construction works at the mine when temporary flooring caught fire, the emergency services told TASS. Extremely high temperatures were preventing rescuers from going deeper and reaching the miners earlier.
It took rescuers several attempts to finally discover the bodies. The operation concluded on Sunday morning with no survivors.
While fire crews are battling the blaze, Russia’s Emergencies Ministry has deployed additional forces of specially trained mine rescuers from nearby regions. The local prosecutor's office has launched a criminal probe, suspecting fatal safety rules violation.