The accident happened when the pillars supporting a fuel tank at a power plant began to sink. The area is built on permafrost which has been melting as the climate warms.
The leaked oil drifted some 12km (7.5 miles) from the accident site, turning long stretches of the Ambarnaya river crimson red.
The spill contaminated a 350 sq km (135 sq mile) area according to state media.
Putin wants to know, why it took two days for him to learn about it.
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.
20,000 tonnes of diesel fuel spilled into the Arctic Circle river.
The volume of the spill is vastly larger than the 2007 Kerch spill, which involved 5,000 tonnes of oil, Alexei Knizhnikov of the World Wildlife Fund said.
