The Russian military said Thursday that it has deployed warplanes armed with state-of-the-art hypersonic missiles to the country’s Kaliningrad region, a move that comes amid soaring tensions with the West over Moscow’s action in Ukraine.

Russia’s Defense Ministry said three MiG-31 fighters with Kinzhal hypersonic missiles arrived at the Chkalovsk airbase in the Baltic Sea enclave as part of “additional measures of strategic deterrence.”

The ministry said the warplanes will be put on round-the-clock alert.

A video released by the Defense Ministry showed the fighters arriving at the base but not carrying the missiles, which were apparently delivered separately.

The deployment of Kinzhal missiles to Kaliningrad as Russia’s campaign in Ukraine nears the sixth-month mark appeared intended to showcase the Russian military’s capability to threaten NATO assets. The region borders NATO members Poland and Lithuania.

Read more: Independent