Russia has for the first time released full declassified footage of the Soviet Union's monster nuclear bomb known as the 'Tsar Bomba' hydrogen bomb (codenamed "Ivan").

Widely considered to be the most powerful nuclear weapon ever created and tested, it was detonated 4,000 meters above a sparsely populated archipelago in the Barents Sea on Oct. 30, 1961 as part of a secretive test nevertheless detected by US intelligence.