A third Japanese citizen has been arrested in China, Japan's top government spokesman said on Friday, in addition to two others arrested earlier this year for spying.
Chief Cabinet Secretary Yoshihide Suga told a regular news conference that the woman, who had been taken into custody in Shanghai in June, was formally arrested last month. He gave no further details, including whether she was suspected of spying.
Chinese Foreign Ministry spokesman Lu Kang said the relevant case was being investigated "in accordance with the law."
Without elaborating, Lu told a daily news briefing, "We have already reported the situation to the Japanese side."
In September, China said it had arrested two Japanese citizens for spying, and a Chinese embassy official in Tokyo later confirmed that two others were being held.
Suga said the fourth was a man, said by Japanese media to have been helping people flee North Korea, who was taken into custody in June and was now under criminal detention.
Suga reiterated that Japan did not engage in spying in any country, but he declined further comment on the specific cases.
Chinese President Xi Jinping has overseen a tightening of already strict security laws and regulations, including setting up a new national security commission and renaming the national security law, which took effect in 1993, as the Counterespionage Law.
In 2010, four Japanese nationals were temporarily detained in China on suspicion of entering a military zone and taking photographs without permission. The detentions came at a time of escalating tensions between Tokyo and Beijing.
Chinese ties with Japan have long been troubled by a territorial dispute and what Beijing sees as Tokyo's failure to properly atone for wartime atrocities, as well as regional rivalry and mutual military suspicious. But relations have improved since Abe and Xi met in November 2014.