Chinese courts have ruled that a Japanese government agency was involved in spying activities in at least three of four cases last year in which Japanese nationals were sentenced to prison for espionage in China, The Yomiuri Shimbun has learned.
The Japanese government has persistently denied allegations that it has dispatched spies to foreign countries.
The Chinese government enacted a counter-espionage law in November 2014 that stipulates the responsibility of Chinese citizens to co-operate with spying investigations and other operations.
The arrests of the Japanese citizens are thought to be connected to China's escalated campaign to uncover spies.
A Chinese court sentenced a 54-year-old man from Aichi Prefecture to 12 years in prison in July 2018 after his arrest in Wenzhou, Zhejiang Province, in May 2015 on spying and other charges.
According to sources knowledgeable about Japan-China relations, the court ruled that the man had monitored China Coast Guard vessels from the Nanji Islands off Wenzhou and had provided information to a Japanese government agency. The ruling added that the man had rented a condominium on one of the islands and took many photographs of China Coast Guard ships from the condo.
The East Sea branch of the China Coast Guard in Shanghai, which has jurisdiction over the area around the Nanji Islands, is also said to have been granted authority by Beijing over waters around the Senkaku Islands in Okinawa Prefecture.
In June 2015, it was learned that a project was under way to build a large-scale coast guard base in Wenzhou's coastal area. The city of Wenzhou and the China Coast Guard discussed the project at a meeting whose contents were later disclosed. China is thus believed to have been highly sensitive about the behaviour of foreign nationals around that time.
In another case, a Chinese court said that a Japanese organisation had engaged in spying activities in a July 2018 ruling concerning a 58-year-old man from Kanagawa Prefecture. The man was detained in May 2015 in Dandong, Liaoning Province.
Another court issued a similar finding last December when it ruled on the case of a 58-year-old female Japanese language school executive who was detained in Shanghai in June 2015.
At least eight Japanese nationals have been arrested and charged with spying since 2015.