BEIJING--China has detained a Japanese man in his 50s for unknown reasons since July in Changsha, the capital of Hunan province, Chief Cabinet Secretary Yoshihide Suga confirmed on Nov. 27.

Japanese government sources said the man is apparently being held by China’s national security authority.

Japanese Embassy staff in Beijing have talked with the detained man and contacted his family members, the Foreign Ministry said, adding that he was in good health.

China in recent years has tightened security against information-gathering activities by foreigners.

The country enacted an anti-espionage law and enforced a national security law from 2014 until 2015 to crack down on intelligence-gathering activities.

Since 2015, at least 15 Japanese have been detained in China over suspected violations of the anti-spying laws. Of them, nine have received prison sentences of three to 15 years.