The Russian Ministry of Defence (MoD) is set to induct an additional S-400 Triumf air defence missile system regimental set into its service this year.

Russian Aerospace Defence Forces spokesman colonel Alexei Zolotukhin was quoted by Sputnik International as saying: "In 2015, one of the air defence missile system regiments in the Moscow region… will adopt into service the modern long-range air defence missile system S-400 Triumph."

The new regimental set represents the fourth unit as three S-400 regiments are currently deployed near Moscow in the cities of Dmitrov, Zvenigorod and Elektrosta.

The S-400 Triumf is an upgraded version of the S-300 missile system. It is a long-to-medium-range surface-to-air missile system, and is designed to intercept a range of ground-based and airborne targets. These include stealth aircraft, strategic carriers, and cruise and ballistic missiles at a distance of 400km.

Almaz/Antei Concern of Air Defence is behind the design of the system, which is code-named the SA-21 Growler. The system features three different missiles, including the extremely long-range 40N6, 48N6 long-range and a 9M96 medium-range missile.

"The S-400 Triumf is an upgraded version of the S-300 missile system."

Sputnik International had earlier reported that MoD intends to have 28 S-400 regiments by 2020. These will each comprise two or three battalions featuring four systems each, primarily in maritime and border regions.

The system is expected to form the cornerstone of Russian air and missile defence by 2020. Nine regiments are already deployed across the country as of December 2014.

Apart from Russia, the system has also attracted interest from a number of foreign countries, including Saudi Arabia, Belarus, and Turkey, as reported by Vedomosti.

In November 2014, Russia state-arms-exporter Rosoboronexport and the Chinese Defence Ministry reportedly signed a $3bn contract for the supply of at least six S-400 battalions.