"In accordance with the decision of the Commander-in-Chief of the Russian Armed Forces snap exercises are being conducted by troops of the Southern and Western military districts," Defence Minister Sergei Shoigu was quoted as saying in a statement.

The drills involve nearly 150,000 personnel including airborne troops and marine infantry of the Northern and Pacific Fleets, the defence ministry said.

The exercises also involve more than 400 aircraft and over 100 vessels and will be conducted in the Black and Caspian Seas, among other places.

The drills aim to test the Russian army's readiness to ensure "security in Russia's southwest where a serious threat of terrorism remains" as well as prepare for the Caucasus-2020 war games, the defence ministry said.

Earlier this month Putin, 67, oversaw a controversial vote that amended the constitution to allow him to serve two more six-year terms after his mandate expires in 2024.