The relevant order was handed over by the commander of the 4th Air and Air Defense Army, Lt. Gen. Viktor Sevostyanov, to a commander of the air defense regiment.
The S-400 battalion has been deployed and started monitoring the airspace.
According to Sevostyanov, the deployment of forces would contribute to the security of Crimea and the major part of the Krasnodar Territory, after the first battalion of the advanced missile systems was deployed near the city of Feodosia in January 2017.
The S-400 systems put on combat duty in 2018 would primarily protect the airspace over the border with Ukraine, a Crimean security source told Sputnik.
Commenting on the deployment, Kremlin spokesman Dmitry Peskov said Wednesday that Russia's taking measures to ensure its security should not be perceived as a threat to anyone.
The deployment was announced in wake of the USS Carney Tomahawk-cruise capable destroyer arrival in Ukraine's port of Odessa, situated less than 200 km away from Russia's Crimea, and about 300 km from Sevastopol, home base of Russia's Black Sea Fleet. The visit was the first by a NATO vessel in 2018, and is expected to last until January 11.
S-400 Triumf (NATO reporting name SA-21 Growler) is Russia's most advanced surface-to-air missile system that has a range of 400 kilometers (248 miles) and is capable of tracking and destroying all existing aerial targets, including ballistic and cruise missiles.