Russian media has said that the country's navy will arm up to six of its submarines with Poseidon nuclear torpedoes.
The torpedoes will be first deployed aboard the converted nuclear-powered submarine Belgorod, and are reputed to have a strength of two megatonnes.
The Poseidon is thought to be laced with radioactive isotopes, which could produce long-term fallout and render thousands of kilometres of land uninhabitable for decades.
