Russian forces have started the first stage of exercises that involve "practical training in the preparation and use of non-strategic nuclear weapons," the Defence Ministry said on Tuesday.
President Vladimir Putin ordered the drills earlier this month. Moscow has linked them to what it calls "militant statements" by Western officials which it said created security threats for Russia.
Russia's Foreign Ministry has cited comments by French President Emmanuel Macron, who floated the possibility of sending European troops to fight Russia in Ukraine, and British Foreign Secretary David Cameron, who said Ukraine had the right to use weapons provided by London to strike targets inside Russia.
Security analysts say the exercise is designed as a warning signal by Putin to deter the West from wading more deeply into the war in Ukraine, where it has provided weapons and intelligence to Kyiv but refrained from sending troops.
The Defence Ministry said the first stage of the exercise involved Iskander and Kinzhal missiles.
It is aimed at ensuring that units and equipment are ready for "the combat use of non-strategic nuclear weapons to respond and unconditionally ensure the territorial integrity and sovereignty of the Russian state in response to provocative statements and threats of individual Western officials against the Russian Federation," the ministry said.
The drills involve missile forces in Russia's Southern Military District, which lies adjacent to Ukraine and also includes parts of Ukraine that Russia now controls.
Belarus, where Russia said last year it was deploying tactical nuclear weapons, will also be involved in the exercises, the two countries have said.
Tactical, or non-strategic, nuclear weapons are less powerful than the strategic arms designed to wipe out whole enemy cities, but they nevertheless have vast destructive potential.
(Writing by Mark Trevelyan and Maxim Rodionov; editing by Mark Heinrich and Gareth Jones)
