Leaked Pentagon documents have seemingly revealed a "doomsday torpedo" being developed by Russia.

"Kanyon" - or "Ocean Multipurpose System Status-6" as it is known in Russia - is a nuclear missile that would be kept in Russia's underwater arsenal. It is allegedly capable of nuking the entire coast of a nation, leaving it uninhabitable for at least 100 years.

The nuclear torpedo was reported in 2015 by the Washington Free Beacon. A Russian television station also reported on the Kanyon missile in the same year.

A Nuclear Posture Review released in January has confirmed the existence of the torpedo (at least in the United States' eyes). It would be capable of travelling 6,200 miles at a maximum underwater depth of 3,280 feet. It would travel at 100 knots (115 miles per hour), according to the leaked documents.

The range would put the Kanyon missile in range from Russia's east coast to the United State's west coast.

Not only would the missile have adequate range, it would also be roughly seven times as powerful as the nuclear bomb dropped on Hiroshima. The Kanyon missile is a 100-megaton bomb, compared to the 16-megaton bomb that devastated Japan in World War II.

The torpedo is also coated in the radioactive isotope Cobalt-60, which is what makes bombed areas uninhabitable for a century. According to Popular Mechanics, if the Kanyon torpedo were to be dropped on New York City, it would kill around eight million people instantly and severely injure a further six million.

The torpedo is reportedly so big, it needs to be carried externally by submarines.

The Nuclear Posture Review identified China and Russia has potential threats. It also raised concern about a Russian protocal to launch small nuclear missiles aimed at European countries in an effort to "escalate to de-escalate".