A source told TASS news agency the Poseidon drone will be able to carry nuclear weapons of up to two megatonnes.
The drone will operate at under-sea depths of more than 1 kilometre, and will have a speed of between 60 and 70 knots.
The source said: “It will be possible to mount various nuclear shares on the ‘torpedo’ of the Poseidon multipurpose seaborne system, with the thermonuclear single warhead.
They added it will “have the maximum capacity of up to two megatonnes in TNT equivalent”.
The Poseidon is “primarily designed to destroy reinforced naval bases of a potential enemy,” the source said.
The development of the drone was revealed by Putin in a State of the Nation address in March.
The Russian President said the machine would have “hardly any vulnerabilities” and would carry “massive nuclear ordinance”.
“There is simply nothing in the world capable of withstanding them.”
The name Poseidon was chosen after open voting on the Russia’s Defence Ministry website.
TASS news agency has not been able to confirm the information provided by the source.
One physicist has said a machine of this magnitude could cause as much damage as the tsunami that hit Japan in 2011.
Rex Richardson told Business Insider: “A well-placed nuclear weapon of yield in the range 20 MT to 50 MT near a sea coast could certainly couple enough energy to equal the 2011 tsunami, and perhaps much more.
“Taking advantage of the rising-sea-floor amplification effect, tsunami waves reaching 100 meters [330 feet] in height are possible.”
The tsunami in 2011 resulted in more than 15,000 deaths in Japan.
It was caused by an earthquake that topped 9.0 in the Richter Scale.