Russia on Wednesday announced the arrest of a Chinese national who was allegedly trying to secure secret documents on S-300 missile systems while posing as an official interpreter.

The Federal Security Service (FSB) said the arrest was made on October 28 last year but did not explain why it had failed to report the incident.

The announcement was made just a week before Prime Minister Vladimir Putin begins a two-day state visit to Beijing aimed at reaffirming the neighbours' joint diplomatic clout and economic importance.

The FSB domestic security service identified the man as Tong Shengyong and said his case had been forwarded by prosecutors to the Moscow City Court on Tuesday.

"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 tried to purchase his data from Russian nationals. The espionage charge carries a prison sentence of 10 to 20 years.

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 Beijing has more recently launched the development of its own missile systems similar to those it used to purchase from Moscow.

Putin will in a week visit Beijing for two days for talks with counterpart Wen Jiabao and President Hu Jintao in his first foreign trip since he announced plans to return next year to the Kremlin post he has already held in 2000-2008.

China and Russia have enjoyed close diplomatic and trade relations in the past decade while seeking to put behind them the border and other disputes that simmered in the Soviet era.

The two this week jointly vetoed a UN Security Council resolution condemning the Syria crackdown and share a deep-seated suspicion of foreign interference in their internal affairs.

China's growing reliance on its own weapons systems is one area hurting Russia directly as it struggles to keep its Soviet-era clients despite its waning list of modern technology.

The Chinese embassy in Moscow could not be reached for comment but analysts said they found the case mystifying because its delayed announcement and reference to an old weapons.

"The S-300s have been delivered to different countries including China," said Alexander Konovalov of the Institute of Strategic Assessment.

"This is not how it usually happens," he added in reference to the delayed announcement.

The FSB statement said the alleged spy was also trying to secure system repair manuals that apparently were not a part of the Chinese arms purchase contract.