Russia has warned NATO it is prepared to use its entire arsenal, including nuclear weapons, if the Western alliance attempts to cut off the Baltic exclave of Kaliningrad, according to a diplomatic document sent to member states.

The diplomatic memo sent on Wednesday claimed Moscow has “information that NATO is preparing an air and naval blockade of Kaliningrad”.

NATO’s response came through its Secretary-General Mark Rutte, who said that NATO is a defensive alliance and that Russia should “stop the nuclear threats”, calling the document unhelpful.

Rutte also downplayed the seriousness of the threat, saying that “Putin knows that he can never win” in a direct escalation with NATO.

Bordered by Poland and Lithuania, both NATO members, the Russian territory of Kaliningrad sits on the Baltic Sea. The region serves as a major military outpost, housing Russia’s Baltic fleet and nuclear-ready Iskander missile systems.

The exchange comes more than four and a half years into Russia’s full-scale war in Ukraine, as tensions increasingly spill into neighbouring states.

Poland has heightened its air defence posture following alleged incursions into its airspace in recent weeks, while Danish authorities said a Russian warship fired two flares near a Danish military helicopter over the Baltic Sea two weeks ago. (Al Jazeera)