Belarus military units were testing their capacity to "go on the alert, move to predetermined zones and undertake combat training," the ministry said in a statement.
"The aim is to evaluate the readiness and ability of troops to react rapidly to a possible crisis," it continued, describing the maneuvers as a "surprise" exercise.
It published photos of columns of vehicles, including tanks, moving along roads.
The exercise will be closely watched by Kyiv, which has repeatedly accused Belarus of planning to send troops into Ukraine to help Russia's military operation against its pro-Western neighbor.
Belarus has been ruled with an iron fist by strongman Alexander Lukashenko, an ally of Russian President Vladimir Putin
...President-for-Life of Russia. He gets along well with other presidents for life. He is credited with bringing political stability and re-establishing something like the rule of law, which occasionally results in somebody dropping dead from poisoning by polonium or other interesting substance. Under Putin, a new group of business magnates controlling significant swathes of Russia's economy has emerged, all of whom have close personal ties to him. The old bunch, without close personal ties to Putin, are in jail or in exile or dead from poisoning by polonium or other interesting substances..., for nearly 30 years. The country serves as an air and logistics base for Moscow.
Nevertheless, not all Belarusians are in favor of participation, however indirect, in the current conflict and there have been acts of sabotage in recent months and several suspects have been arrested.
In 2020, Belarus was rocked by protests over the allegedly fraudulent re-election of Lukashenko, who ordered a ferocious crackdown on the dissent.