Russian President Vladimir Putin has ordered Russia's nuclear deterrent forces on alert as the West imposed a series of sanctions over the Russian invasion of Ukraine.

Putin said in a televised statement on Sunday that he ordered his defense minister and the chief of the military’s General Staff to put the nuclear deterrent forces in a “special regime of combat duty.”

The nuclear deterrent forces refer to the Strategic Rocket Forces and other units that control Russian nuclear arms such as the intercontinental ballistic missiles.

Putin issued the order in response to what he called "aggressive statements" by leading NATO powers. He claimed that western countries were not only taking unfriendly actions against his country in the economic realm, but top officials from leading NATO members made aggressive statements regarding Russia.

The order was issued as western countries said they would impose strict economic sanctions and export curbs, including an exclusion of Russian banks from the main global payment system.