Vladimir Putin has ordered a state of emergency after 20,000 tonnes of diesel fuel spilled into a river inside the Arctic Circle.
The spill occurred when a fuel reservoir at a power plant near the city of Norilsk collapsed on Friday.
The plant is operated by a division of Nornickel, whose factories in the area have made the city one of the most heavily polluted places on Earth.
During a video conference on Wednesday that was broadcasted on television, Putin lambasted the head of the Nornickel subsidiary that owns the power plant, NTEK, after officials said the company failed to report the incident.