Russian President Vladimir Putin has announced snap military drills on land and in the Black and Caspian Sea, the defense ministry said on Thursday.
The drills began at 7:00 a.m. (0400 GMT) Moscow time in Russia's southern, western and central military districts where troops have been put on combat alert, the ministry said in a statement. Russian television led its news bulletins with images of heavy weaponry and tanks on the move and troops in full combat gear running to grab their weapons from the ammunition storage.
Neighboring Poland reacted by calling an instant briefing of the commands of operational forces and of military intelligence.
The drills which will last until the end of the month will involve a variety of troops, from paratroopers to the Northern Fleet.
The drills come a week after Russia for the first time since it began its operation in Syria used an air base in Iran, and after President Putin lashed out at Ukraine for allegedly sending its military intelligence office to carry out acts of sabotage in Russia-annexed Crimea.
In Poland, which has been wary of Moscow's actions, the defense ministry said Minister Antoni Macierewicz ordered a briefing of the heads of the armed forces' Operational Command, Military Intelligence and Military Counterintelligence. The timing of the briefing was not revealed.
The Operational Command is in charge of the air defense and of reacting to crisis situations.
The ministry also said Poland's military envoy in Moscow has been "invited" to Russia's defense ministry.
Krzysztof Szczerski, an aide to Poland's President Andrzej Duda, said that the military relations between Russia and East European countries are a "game of emotions" that should not be given in to.
He said Poland would monitor the situation.