Belarus and Russia have announced joint military exercises near the Polish border.
A "joint tactical battalion group" with paratroopers from both countries is holding exercises in the Grodno region in western Belarus, the Belarusian Defense Ministry announced on Telegram on Friday.
It justified the move with the "increase in military activity" near the Belarusian border.
Poland has deployed 15,000 soldiers in the area due to the influx of thousands of migrants on the Polish-Belarusian border.
According to Mink, Russian Il-76 military aircraft and Belarusian military helicopters are also involved in the exercises.
According to Russian news agencies, the Ministry of Defense in Moscow said it was a surprise mission to "check the combat readiness" of the troops.
Thousands of migrants, mainly from the Middle East, are currently stuck at the EU's external border in Poland at temperatures around freezing point.
The EU accuses the Belarusian ruler Alexander Lukashenko of deliberately smuggling migrants to the borders of the EU states Latvia, Lithuania and Poland in retaliation for sanctions.