The Russian military has put its S-400 anti-aircraft missile system on combat duty around Moscow. The surface-to-air defence system, which is widely being used in Syria, has been deployed in order to protect the Moscow airspace, said the government.

"As part of re-equipping the Aerospace Forces by modern and advanced missile defence systems another regiment-size set of S-400 Triumf system entered service in one of the Moscow Region's air defence task forces of the Aerospace Forces," said the Russian defence ministry's department of information and mass communication.

It added: "The surface-to-air [SAM] combat squads of the Moscow Region aerospace forces have put the new S-400 Triumph air defence missile system into service, and have gone on combat duty for the air defence of Moscow and the central industrial region of Russia."

Four more such regiments equipped with the advanced missile system are expected to put on duty later this year. The ministry said the S-400 missile systems had undergone drills in the southern region of Kapustin Yar in December before being deployed for active duty.

The ministry further said: "The main task of the anti-aircraft missile troops of the Russian Aerospace Forces is air defence and protecting vital state, military, industry and energy facilities, as well as the Armed Forces troops and transport communications, from aerospace attacks."

The S-400 system, known as SA-21 Growler, is Russia's most sophisticated air defence system and has a strike range of 400kms. The S-400s can track mobile aerial targets including ballistic, cruise and tactical missiles.