Beijing has built what experts believe is a nuclear torpedo that can destroy entire coastal cities with radioactive tsunamis.

It's a new extra-large unmanned underwater vehicle (XLUUV), a nuclear-powered torpedo-like drone resembling Russia's Poseidon.

It uses a disposable reactor for ~200 hours at 30+ knots, then battery power, with potential nuclear armament to trigger radioactive tsunamis against coastal targets.

Details remain classified