The exercises, which are expected to last until February 20 in Belarus, raise concerns in the West that Russian President Vladimir Putin intends to escalate the conflict around Ukraine, where tens of thousands of Russian soldiers are at the border.
"The purpose of the exercise is to train to prevent and ward off external attacks through a defensive effort," the Defense Ministry said in a statement, according to Russian news agency Interfax.
NATO estimates that 30,000 Russian troops are now in Belarus, and according to the alliance, Russia is building up its largest military presence in Belarus since the Cold War.
At the same time, talks continue at the top political level with the aim of stepping down the crisis.
British Foreign Secretary Liz Truss has traveled to Moscow to talk to her Russian counterpart Sergei Lavrov.
On Thursday, British Prime Minister Boris Johnson will also visit NATO Headquarters in Brussels and travel to Poland to meet with Prime Minister Mateusz Morawiecki.
This since Britain promised to send 350 soldiers, in addition to the 100 already sent, to Poland's border with Belarus.
In addition, talks on the conflict in eastern Ukraine will be held on Thursday in the so-called Normandy format, a negotiating forum in which representatives from Ukraine, Russia, Germany and France participate.
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The conflict between Russia and Ukraine - that's how it started