MOSCOW, October 8. /TASS/. Russia did not invite military attaches from NATO countries to attend the main phase of the strategic Russian-Belarusian exercise Zapad-2021 at the Mulino proving ground in a tit-for-tat gesture, Deputy Defense Minister Alexander Fomin said on Friday.

"Military attaches from the NATO countries were not invited to this phase of the exercise in retaliation, because Russian military attaches were not invited to a similar NATO exercise, Defender Europe 2021," Fomin told a news briefing for foreign military attaches.

Russia 42 days ahead of the exercise notified the Organization for Security and Cooperation in Europe (OSCE) of the number of personnel to be involved in the drills, Fomin stressed.

He recalled that taking part in the Zapad-2021 exercise were some 200,000 officers and men, 80 planes and helicopters, 760 pieces of ground military equipment, and 15 combat ships. The exercise was monitored by observers from Vietnam, China, Myanmar, Pakistan and Uzbekistan. Combat drills were conducted at five sites in Belarus and nine in Russia and also in the Baltic Sea.

Earlier, the first deputy chief of the Defense Ministry's Main Directorate for International Military Cooperation, Major-General Yevgeny Ilyuin said that participating in certain episodes of the exercise that fall under the operation of the 2011 Vienna Document will be no more than 6,400 troops. The Vienna Document envisages mandatory invitation of monitors to drills by contingents of 13,000 troops and more.