The man, an employee of the Japanese pharmaceutical company Astellas, was held in March 2023 and placed under formal arrest in October.

He was "sentenced to three years and six months in prison for espionage activities," Kenji Kanasugi, Japanese ambassador to China, told Japanese media after the trial in Beijing.

"It is extremely regrettable that such a guilty verdict was issued," he said.

Five Japanese nationals, including the Astellas official, are in custody or serving prison terms in China, according to NHK.

Tokyo had repeatedly called on Beijing to release them and Wednesday's sentence deals a blow to ties, long frayed over territorial disputes, Japan's colonial history and other flashpoints.

"In light of the sentence, we have once again strongly urged the Chinese side for the early release of the Japanese national concerned in this case as well as others detained," Tokyo's embassy in Beijing said in a statement.

It also urged China "to ensure their legitimate rights and humane treatment during detention, and to improve the transparency of the judicial process".

The detained man has reportedly worked in China for two decades and was previously a senior executive at a major Japanese business lobby in the country.

He was planning to return to his home country before his sudden detention, according to Japan's Kyodo News Agency.

hih-mya/oho/mtp

ASTELLAS PHARMA