Vladimir Putin has ordered that Russia’s nuclear deterrence forces are put on high alert.
Mr Putin said aggressive statements by NATO leaders and economic sanctions against Moscow were behind the decision.
Speaking on state television on Sunday, he said: “As you can see, not only do Western countries take unfriendly measures against our country in the economic dimension – illegitimate sanctions that everyone knows about.
“But also the highest-ranking officials of leading NATO countries are allowing themselves to make aggressive statements in relation to our country.
“For this reason I order the minister of defence and the chief of general staff to put deterrent forces on special combat duty.”