Russia says more than 20 warships and support vessels have departed from their bases in the Caspian Sea and begun training as part of massive combat readiness exercises across the country's southwest.
The military says the snap drill, which kicked off on February 8, will involve up to 8,500 troops and 200 aircraft.
Defense Minister Sergei Shoigu said the maneuvers are intended to check the troops' ability to respond to extremist threats and other challenges.
They involve forces stationed in the Southern Military District, which includes southwestern regions near the border with Crimea -- the Ukrainian peninsula which was annexed by Russia in 2014 -- the North Caucasus, the Black Sea, and the Caspian Sea.
The exercises are the latest in a series of major drills conducted in the past two years amid an increase of tension between Russia and the West.
Based on reporting by Interfax and AP