Russia's Federal Security Service (FSB) has detained a Chinese national they say was trying to gain access to secret information about the S-300 air defense system, the FSB said in a statement on Wednesday.
Tun Shenjun was arrested on October 28, 2010. News of his arrest has onlu just been made public.
"It was established that the Chinese citizen was working for the State Security Ministry, the security agency of the People's Republic of China, as a translator for official delegations and was gathering secret information from Russian citizens about technical and repair documentation for the S-300 missile system," the FSB said.
Russia's General Prosecutor's office filed a criminal case at a Moscow court on October 4.
Russia has supplied the S300 system to China, and Beijing is also licensed to manufacture it.
The S300 has been replaced in Russia with the S400.
The Chinese authorities have yet to comment.