Russian President Vladimir Putin on Tuesday lowered the threshold for a nuclear strike in response to a broader range of conventional attacks, and Moscow said Ukraine had struck deep inside Russia with U.

Russian President Vladimir Putin on Tuesday signed a revised nuclear doctrine declaring that a conventional attack on Russia by any country 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 US counterpart Joe Biden granted Ukraine permission to strike targets deep inside Russia with US-made weapons. Under the updated doctrine issued Tuesday,