MOSCOW, Nov. 22 (Xinhua) -- Russia is taking all necessary measures to protect against the aggressive expansion of the North Atlantic Treaty Organization (NATO), the Kremlin said on Tuesday.

Kremlin spokesman Dmitry Peskov called NATO "an aggressive bloc" at a briefing here, saying that its expansion towards the Russian borders has prompted Moscow to "take all necessary countermeasures."

On Monday, Russian President Vladimir Putin said in a documentary produced by U.S. film director Oliver Stone that it is the "worrisome decision-making" in NATO's eastward expansion that makes Russia to take countermeasures.

Relations between Russia and the West have been souring since the Ukraine crisis in 2014.

Earlier this month, NATO announced the deployment of 300,000 troops in eastern Europe, which can be put on "high alert" in response to increasing tensions between Russia and Baltic states.

Last week, a new NATO headquarters was established in the eastern European country of Hungary, acting as "the Alliance's eyes and ears on the ground, and sharing information with the host nation and higher headquarters in peace time, crisis and conflict."

Viktor Ozerov, chairman of the Defense and Security Committee of Russia's Federation Council, or the upper house of parliament, said last week that Moscow would boost air and missile defenses on its western borders to counter the deployment of the U.S. global missile defense system in Europe.

Russia's readiness to strengthen military power envisions the deployment of S-400 air defense systems and the Iskander-M tactical ballistic missile systems in the Kaliningrad, which is located near the borders with NATO members Poland and Lithuania, Ozerov said.