RUSSIA'S "city killer" submarine has set sail for the first time packed with nuclear drones capable of triggering monster tsunamis. The 604ft Belgorod - which is twice the size of the Royal Navy's Astute-class attack subs - reportedly took to the sea for the first time on Friday. The 14,700-tonne war machine bristles with nuclear-tipped underwater drone torpedoes - each guided by artificial intelligence. The secretive launch came after Vladimir Putin's navy vowed to sink British warships the next time they sail too close to Crimea. The war talk followed a face-off in the Black Sea where HMS Defender was...