S-400 surface-to-air missile systems. S-400 surface-to-air missile systems on streets of St. Petersburg, during preparation of Victory Day parade at Palace Square. Russia, St. Petersburg, on May 5, 2016. (Xinhua/SIPA)

MOSCOW, Jan. 23 (Xinhua) -- Russia is in negotiation on the selling of self-designed S-400 air defense systems with a number of Middle Eastern and Southeast Asian countries, Russian Defense Minister said Tuesday.

"Countries in the Middle East and Southeast Asia have already expressed interest in acquiring the S-400. Negotiations are already underway," Sergei Shoigu said during his ongoing visit to several Southeast Asian countries, according to the ministry's press service.

Potential Middle Eastern buyers include Syria, Iraq, Sudan and Egypt, Russian upper house's Defense and Security Committee Chairman Viktor Bondarev was quoted by Russia's Sputnik News Agency as saying.

Shoigu said that S-400 system's unparalleled performance capabilities was proven by Turkey's decision to purchase four S-400 systems last year, the press service said.

Turkey was the second member of the North Atlantic Treaty Organization to buy Russian air defense systems following the deployment of Russia's S-300 missile complexes in Greece.

Shoigu also confirmed that two S-400 missile complexes are on combat duty at Russia's Hmeymim and Tartus bases in Syria.

The S-400 air defense missile system is considered to be the most advanced of its kind in Russia, capable of defeating targets at a distance of up to 400 km and at an altitude of up to 30 km, according to the defense ministry.