Moscow said it will deploy a motorised division in Kaliningrad, a Russian exclave bordering Poland and Lithuania, according a Russian-government newspaper.
"The increasing concentration of NATO forces in the region creates concerns [...] to overcome this situation, it has been decided to enhance the defence of Kaliningrad Region," according to Rossiyskaya Gazeta.
Despite not naming the exact unit, the newspaper mentions the arrival of a motorised division, the Latvian news agency LETA reported on Wednesday.
Following Russia's aggression against Ukraine, NATO has bolstered its presence in the Baltic states and Poland. US President Donald Trump and his Polish counterpart, Andrzej Duda, agreed earlier this year to deploy additional American forces in Poland to deter Russia.
Meanwhile, US Air Forces in Europe Commander Jeff Harrigian said in September the US has a plan to counter Russian air defences in Kaliningrad. Moscow criticised the statement, saying Russia considers it "a threat".
Read more: Russia deploys additional air defences in Kaliningrad
In November, an armoured US battalion arrived in Lithuania on a rotational deployment, which caused an outcry in Moscow and Minsk, with Belarus claiming it would deploy additional troops near the Lithuanian border.
The NATO summit in London on December 3-4 reconfirmed the threat of Russia.
Read more: NATO declaration reflects Baltics’ Russia worries