Photo/Illutration China has detained 17 Japanese nationals since 2015 on suspicion of them undermining its national security. (Asahi Shimbun file photo)

BEIJING--Chinese authorities have upheld a 12-year prison sentence for a Japanese man convicted of espionage, sources said.

Rejecting the defendant’s appeal on Nov. 3, a high court in Hunan province ruled that he had undermined China’s national security.

The man was detained in the provincial capital of Changsha in July 2019. Details of his allegations have not been disclosed.

The man, in his 50s, is in good health and maintains contact with Japanese Embassy officials.

Since 2015, Beijing has detained 17 Japanese nationals on charges of espionage and other offenses that pose a threat to national security.

Five of them remain in custody, including an employee of Tokyo-based Astellas Pharma Inc., who was officially arrested in October.

The latest verdict marks the third final judgment handed down to these five individuals.

Foreign businesses operating in China have expressed concerns over a revised anti-espionage law enacted in July, saying the new regulations lack clear definitions of corporate spying.