Evidence

Searches found several outlets reporting this. Meduza, Nasha Niva, European Pravda (Ukrainska Pravda) and New Voice of Ukraine all say the Russian embassy in Ireland posted the warning on social media. The warning reportedly says Russia would be ready to use its entire arsenal, including nuclear weapons, if NATO countries tried to isolate Kaliningrad. The same outlets say Reuters obtained a Russian diplomatic note sent to NATO with the same warning. The note reportedly also describes NATO's course as dangerous and reckless, with a high risk of direct armed conflict. NATO's written reply rejected the threat. It said its activities do not threaten Russian territory and urged Russia to stop its nuclear rhetoric. I did not open the original Reuters article. Its content comes only through secondary outlets that cite it. I found no Reuters, AFP, Bellingcat or EUvsDisinfo fact-check, which is expected because this is a report of a statement and not a disputed media item. The claim is that Russia made the statement, and multiple outlets corroborate that. The embassy's reference to NATO blockade preparations appears to rest on unspecified reports, and I found no evidence of such plans.