Russian President Vladimir Putin has signed a revised nuclear doctrine declaring that a conventional attack on Russia by any nation that is supported by a nuclear power will be considered a joint attack on his country.

President Vladimir Putin has updated Russia’s nuclear doctrine, two days after his American counterpart Joe Biden granted Ukraine permission to strike targets deep inside Russia with US-made weapons.

Putin will share Russia's nuclear deterrence with its allies—mirroring NATO's "attack on one member is an attack on all" doctrine.