MOSCOW, April 13. /TASS/. China has purchased S-400 missile defense systems from Russia, director general of Russia's major arms exporting company Rosoborobexport Anatoly Isaykin has told the Kommersant daily in an interview. Isaykin refused to disclose terms of contract but confirmed that China had become the first buyer of the cutting-edge air defense system. He noted that it emphasizes the strategic nature of Russian-Chinese relations.