Russia, Serbia, and Belarus are holding joint military exercises near the Belarusian border with NATO member Poland.
At an opening ceremony on June 6, Russian Colonel Aleksei Sgibnev said the Slavic Brotherhood-2017 drills show that "the three states have achieved closer cooperation and are preparing to together fight the greatest evil of our time: international terrorism."
More than 300 Russian, 400 Belarusian, and 50 Serbian troops are taking part in the maneuvers, which are scheduled to end on June 14.
Russian Il-76MD military transport planes and Belarusian military aircraft are taking part in the exercises.
The drills near Poland, a NATO and European Union member, began a day after Montenegro became the Western military alliance's 29th member.
These are the third Slavic Brotherhood drills held by the three countries.
The first were held in 2015 in Russia's Krasnodar Krai, which is close to Western-leaning Georgia and Ukraine's Russian-controlled Crimean Peninsula.
The second were held in November 2016 in Serbia, while NATO was staging a civil emergency drill in neighboring Montenegro.