Chinese prosecutors have begun procedures to decide whether to indict a Japanese businessman who has been detained for a year on suspicion of espionage.

The man in his 50s is an employee of major Japanese drug maker Astellas Pharma. He was detained in Beijing in March last year and was formally arrested in October.

Sources with a knowledge of Japan-China relations say the prosecutors began the process on Monday. They are expected to take up to six-and-a-half months to make a decision. They may also carry out additional investigations during the period.

If the man is indicted, the case will be brought into court. An early release would then become more difficult to arrange. The Japanese embassy says it will continue to strongly urge China to quickly release him.

Japanese embassy staff are visiting the man on a regular basis at a detention facility in Beijing. The new Japanese ambassador to China, Kanasugi Kenji, met with him in January right after he took office.

A number of foreign nationals, including Japanese citizens, have been detained by China for alleged spying activities.

Concerns are mounting among foreign businesses operating in China, because it is unclear what activities are illegal under Chinese law.