Russian defense ministry officials said on Monday that President Vladimir Putin has ordered preparations for an exercise simulating the use of tactical nuclear weapons. They said they want to maintain the readiness of combat units and non-strategic nuclear weapons.

Ministry officials said forces from the Southern Military District will take part in the drills. They said the exercise is in response to "provocative statements and threats made by certain Western officials." They said they want to ensure Russia's territorial integrity and sovereignty.

Kremlin spokesperson Dmitry Peskov said some Western leaders have spoken about "an intention to send armed contingents" to Ukraine. "This is an entirely new round in the escalation of tension," he said.

Putin is starting his fifth term as president on Tuesday. On Thursday, his troops will mark the anniversary of the end of World War Two with the celebration of Victory Day.

A spokesperson for Ukraine's military intelligence unit, Andriy Yusov, condemned Russia's plans. He said that "nuclear blackmail" is a constant practice of Putin's regime.