Russia said today it had arrested a Chinese national who allegedly was trying to secure secret documents about the country's S-300 missile systems while posing as an official interpreter.

The Federal Security Service (FSB) said the initial arrest had been made on October 28, 2010 and refused to explain why it had previously failed to report the incident.

It identified the man as Tong Shengyong and said that his case had been forwarded by prosecutors to the Moscow City Court.

"The investigation established that the Chinese national (was) working on assignment from the Ministry of Public Security of the People's Republic of China," FSB said in a statement.

It said the man had posed as an interpreter for "official delegations" and attempted to purchase his data from Russian nationals.

The S-300 system is an older version of Russian surface-to-air missiles that Moscow has produced since the Soviet era and has since replaced with the more modern S-400.

China has a decades-long history of military ties with Russia and is one of its largest arms purchasers alongside India.

But it has more recently begun the development of its own missile systems similar to those it used to purchase from abroad.