President Vladimir Putin declared a state of emergency last Wednesday, several days after 21,000 metric tons of diesel leaked from a collapsed fuel tank outside the city of Norilsk.The pollution now risks running north into the Arctic Ocean.

The exact reason of the leak is yet to be established, but a statement from Norilsk Nickel company, which operates the site suggests it could have been caused - worryingly - by collapsing permafrost.

A spill that dumped thousands of tons of diesel fuel into the Russian Arctic earlier this year was caused by violations during construction and operation of a storage tank, not permafrost melt, according to a preliminary investigation. 

While mining giant Nornickel has said the local ecosystem is "satisfactory," environmentalists paint a different picture.

Light diesel leaked from an oil company facility into Ramfjorden outside Tromsø, and police, fire crews, Kystverket and the acute pollution committee are working to contain it.