Russia has warned NATO that it is prepared to use “the entire arsenal of forces and capabilities” at its disposal, including nuclear weapons, if the alliance attempts to isolate the Kaliningrad region from the rest of Russia, according to a diplomatic document seen by Reuters.

In the document, Moscow accused the alliance of pursuing a “dangerous and reckless course” that carries “high risks of the outbreak of a direct armed conflict.” It also referred to the possibility of Russian strikes against decision-making centers in alliance member states “right from the outset.”
NATO’s written response, also seen by Reuters, said the alliance is defensive and obliged to counter threats to its members from all directions.

Kaliningrad, home to Russia’s Baltic Fleet, is an exclave bordered by NATO members Poland and Lithuania, with no land connection to the rest of Russia.