Defence chiefs are on alert after Russia developed a “doomsday” underwater drone capable of travelling 6,000 miles and blowing up an entire coastal city.
The drone, effectively a giant torpedo codenamed Status-6, is part of a growing arsenal being developed by Vladimir Putin.
Details of the drone – also known as Poseidon – come days after the Royal Navy had to escort nine Russian warships out of UK waters.
Poseidon, which is designed to be launched from the world’s longest submarine the Belgorod, travels at up to 100 knots and can dive to 1,000m.
It would hug the seabed to avoid detection before arriving off a pre-set target.
Its two-megaton nuclear warhead would detonate a blast equivalent to 2,000 tons of TNT, which would have a radius of four miles and be capable of killing and injuring millions.
Poseidon is one of several new Russian weapons including a missile that flies at a mile per second.