The Russian President Vladimir Putin has ordered his country’s strategic nuclear forces to high alert, as the Ukraine crisis escalates.
He told defence chiefs it was because of "aggressive statements" by the West, amid widespread condemnation of his invasion of Ukraine. The announcement does not mean Russia intends to use the weapons.
The US immediately condemned his decision calling it an "unacceptable escalation".
Recently Mr Putin had warned that "whoever tries to hinder us" in Ukraine would see consequences "you have never seen in your history". Those words were widely interpreted as signalling a threat to use nuclear weapons if the West stood in his way.
The Russian President ordered his defence minister and the chief of the military's general staff to put the nuclear deterrent forces on a "special regime of combat duty".
Clive Myrie in Kyiv presents BBC News at Ten reporting by Steve Rosenberg in Moscow and Sarah Smith in Washington.