BEIJING (Reuters) - Chinese authorities on Monday arrested a Japanese citizen suspected of spying, local state media said. The arrest was made in the port city of Dalian in the northeastern Liaoning province, which borders North Korea, the official Dalian Daily s online report said. The report said Ken Higuchi was being investigated by the Dalian City National Security Bureau on suspicion of spying against China, and that prosecutors had approved his arrest. The character given for Higuchi s first name could also be the names Takeshi or Takeru. It was unclear from the report, however, whether Higuchi was a new case or whether he had been detained earlier, and the latest development was his formal arrest. China detained six Japanese nationals in March on suspicion of illegal activities. Four of the six returned to Japan in July, three of whom were there doing geological research into hotsprings, according to their employer. China s foreign ministry also in July said that a single Japanese citizen was being investigated on suspicion of harming China s national security. Reuters was unable to contact Japan s foreign ministry by telephone. Monday was a national holiday in Japan. China s relationship with Japan has been strained for decades over the legacy of Japan s wartime aggression, while a maritime territorial dispute over small islands in the East China Sea has in recent years added to the suspicion between the two sides. In 2010, four Japanese nationals were detained in China on suspicion of entering a military zone and taking photographs without permission. At least two Japanese citizens were arrested on suspicion of espionage in 2015. Last year, China said it was investigating a Japanese citizen on suspicion of endangering national security. 