Russia's defence ministry on Monday said its nuclear missile forces and Northern and Pacific fleets had been placed on enhanced combat duty, the Interfax news agency reported, in line with an order the previous day from President Vladimir Putin.
Defence Minister Sergei Shoigu told Putin that "shifts on duty at the command posts of the Strategic Missile Forces, the Northern and Pacific Fleets, and the Long-Range Aviation Command began to carry out combat duty with reinforced personnel," Interfax quoted the ministry as saying.
Putin on Sunday ordered his military command to put Russia's deterrence forces - which include nuclear arms - on high alert, citing what he called aggressive statements by NATO leaders and Western economic sanctions against Moscow.
The move drew condemnation in the West, with the United States describing it as an escalation. A senior U.S. defense official said it was "putting in play forces that, if there's a miscalculation, could make things much, much more dangerous."
It came as Russian forces ran into tough Ukrainian resistance after invading Ukraine last week in what Putin has described as a special military operation to demilitarise the country.
Putin has justified the invasion by saying "neo-Nazis" rule Ukraine and threaten Russia's security - a charge Kyiv and Western governments say is baseless propaganda.
(Reporting by Reuters in Moscow; Editing by Jon Boyle and Peter Graff)
