A nuclear-powered underwater drone capable of destroying enemy naval bases and causing huge tsunamis is under construction in Russia, according to a state news agency.

The Poseidon will be able to carry a nuclear warhead with a capacity of up to two megatonnes, a source told TASS.

The source said: "It will be possible to mount various nuclear charges on the 'torpedo' of the Poseidon multipurpose seaborne system, with the thermonuclear single warhead... to have the maximum capacity of up to 2 megatonnes in TNT equivalent."

With its nuclear munition, the underwater drone "is primarily designed to destroy reinforced naval bases of a potential enemy," the source said.

The drone will have a speed of 60-70 knots and will be operational at a depth of more than 1km.