NATO denied Russian claims Wednesday that it was planning to deploy massive numbers of troops near the country's border.

"I totally dismiss claim by dep defense minister Antonov that NATO plans to deploy large military contingents close to Russia's borders," said NATO Deputy Secretary General Alexandre Vershbow on twitter.

His tweet was in response to comments by Russian Deputy Defense Minister Anatoly Antonov at a news conference earlier in Moscow.

"Russia has taken note of the plans by certain members of the alliance to deploy large military contingents on their territories close to our borders," Antonov was quoted as saying by Interfax news agency.

Vershbow said that "NATO's core task is collective defence. We're taking legitimate steps to deal with instability created by Russia's illegal actions".

To reassure East European members of the alliance, in particular the Baltic states, Poland and Romania, NATO in early March decided to temporarily deploy AWACS reconnaissance aircraft.

The AWACS -- Airborne Warning and Control System -- will overfly Poland and Romania as part of alliance efforts to monitor the crisis in Ukraine, NATO said.

The United States has also sent six F-15 fighter-bombers, a dozen F-16 fighter jets and three transport aircraft to Poland. A guided missile destroyer, the USS Donald Cook, is due in the Black Sea in the coming days.

Other European nations, including Britain and France, have offered to send aircraft to the area if requested by NATO.

NATO's chief Anders Fogh Rasmussen on Tuesday warned Russia against intervening further in Ukraine, urging Moscow to "step back" after pro-Kremlin militants seized government buildings in several cities in the east.

"Russia's illegal aggression against Ukraine is the greatest challenge to Europe's security in a generation," Rasmussen said.

NATO has suspended much of its cooperation with Russia, with Russian officials no longer welcome since this week at its Brussels headquarters, the exception being the Russian ambassador, his deputy and two members of his team.