Russian nuclear submarine
Leaked Pentagon documents illustrate a Russian underwater drone that is capable of carrying a 100-megaton warhead REUTERS/Yuri Maltsev

A recently leaked Pentagon report has confirmed the presence of a Russian undersea drone submarine capable of being outfitted with a 100-megaton nuclear warhead.

The drone, dubbed Autonomous Underwater Vehicle or AUV, has been rumoured in the past but this is the first time the Pentagon has acknowledged its existence. The weapon was detailed in a draft of Nuclear Posture Review, obtained and published by the Huffington Post.

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The report, which highlights nuclear capabilities of countries like the US, Russia, North Korea and China, stresses on the fact that Kremlin has been advancing its conventional nuclear arsenal while developing new weapons and technologies for their deployment.

"In addition to modernising 'legacy' Soviet nuclear systems, Russia is developing and deploying new nuclear warheads and launchers. These efforts include multiple upgrades for every leg of the Russian nuclear triad of strategic bombers, sea-based missiles and land-based missiles," the document reads.

"Russia is also developing at least two new intercontinental range systems, a hypersonic glide vehicle and a new intercontinental, nuclear-armed undersea autonomous torpedo."

The drone was illustrated in a chart mentioning several nuclear capable vehicles developed by Russia over the past 10 years. The weapon, officially dubbed Ocean Multipurpose System Status-6, can go up to 6,200 miles at a maximum speed of 56 knots and even descend into the depths by going 3,280 feet below sea level, Defense News reported.

So far, the weapon has been tested just once, according to a report in Washington Free Beacon. On 27 November 2016, a Sarov-class submarine launched the drone to validate its working, following which US Intelligence detected it.

Rubin Design Bureau, Russia's largest submarine manufacturer and the creator of this drone, has assured that the drone can be launched from at least two different classes of nuclear submarines, including the Oscar-class.

The Nuclear Posture Review report highlights America's interest in advancing its nuclear stockpile — air, sea, and ground-based missiles— to match with Russia and other countries. However, there is no word on nuclear-capable underwater vehicles like the one from Russia.