Hundreds of giant “gas bombs” could explode and form massive craters in the Arctic – potentially disrupting energy supplies to Europe.
Russia has identified up to 430 of the bulging moulds, leading to calls for urgent military-style action to spike them before any future blasts.
So far 17 large holes have formed since 2014 in the Yamal and Gydan peninsulas in Siberia due to vast methane eruptions in thawing permafrost.
Professor Vasily Bogoyavlensky, of the Russian Oil and Gas Research Institute in Moscow, is now calling for immediate action.
He warned many of the 430 craters lie close to key natural gas installations which are part of a network supplying western Europe.
Some 7,185 mounds have been identified from satellite image analysis, with up to 6% of them being “really dangerous”.
He identified high risk sites near three gas fields on the Yamal peninsula – North-Tambey, South-Tambey and Western-Seyakha.
The professor said the dangerous mounds must be “cut open with gas being pumped out”, indicating it was a complex job for the military.
He added: “Of course it must be done very carefully, it is sappers’ work, as these phenomena can be called ‘gas bombs’.”
Only three of the 17 known eruptions were witnessed, with each causing an explosion with flames.
Prof Bogoyavlensky added: “We believe the ignition was caused by electrostatic discharges, which adds to the danger of these mounds.”
He revealed a local woman, who visited one of the craters daily, had a lucky escape when it exploded.
Prof Bogoyavlensky said: “On the day of the explosion she felt some tremor, she described it as if the earth was breathing.
“She quickly left the place just in time before it exploded.
“If she had shown more curiosity, she would have been killed by this explosion and we would have the first victim.”
Reindeer and dogs also “fled in terror” during the 2017 eruption.
The mounds form as methane migrates from deeper layers through faults in thawed zones to fill cavities formed in the permafrost.
Usually such cavities are covered by seals of permafrost up to 30ft thick.
The size increases under growing pressure from the gas and eventually blows up the seal with massive chunks of frozen rock and soil thrown as far as 2,950ft.
The gas-filled mounds can increase in size up to almost 3ft a year before exploding.
An expedition to one of the latest sites found it was around 131ft deep when it first formed.
At some exploded craters, methane continues to seep out after the explosions.
When the mysterious holes first appeared in 2014 there were claims they were caused by Russian missile tests, aliens or were man made as ‘pranks’.
But although they have widely been seen as being caused by climate warming, experts say this link is still being studied.