Giant hole, thought to have been caused by methane release, is biggest of its kind discovered in Russia’s Yamal peninsula. It is the 17th crater of its kind to be found and documented in Yamal since 2014.

Usually polar bears feed on seals and young walruses, or scavenge the carcasses of whales. If these are in short supply they kill reindeer, muskox, geese and apparently, fox.

Locals say they saw flames and smoke as a major bubble of methane blasted below the surface and created another sinkhole in the Russian Arctic peninsula.

The aim is to give warnings over seismic activity that could lead to the sudden formation of new craters, which could potentially damage key industrial infrastructure.