Japan's embassy in China confirmed Thursday that one of its citizens had been formally arrested, months after Beijing said it had detained the man on spying allegations.
Chinese authorities frequently hold foreign nationals suspected of crimes for long stints before declaring them officially under arrest.
The man, an employee of the Japanese pharmaceutical company Astellas, was held in March, with Beijing saying he was "suspected of engaging in espionage activities".
An official at Tokyo's embassy said Thursday that Chinese authorities had escalated his detention into a formal arrest.
"We can confirm that the Japanese national detained in March has been arrested," the official said in a statement to AFP.
In a separate statement, Tokyo's Chief Cabinet Secretary Hirokazu Matsuno said Thursday that the man "was arrested in mid-October".
"We have called on China for his early release at various levels and various opportunities. We will continue this effort," he said at a regular news briefing.
A Japanese diplomat has visited the man and the government is "in touch with his family", Matsuno said.
China's foreign ministry on Thursday declined to confirm the arrest, referring a question about the case to the "competent authorities".
"This Japanese citizen, suspected of engaging in espionage activities, has been subjected to criminal coercive measures by relevant Chinese authorities in accordance with the law," ministry spokeswoman Mao Ning said.
"As a country ruled by law, China will handle this case in accordance with law and protect the legitimate rights and interests of this person," she said at a regular briefing.
The arrested 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.
Australian journalist Cheng Lei was held by China's national security services from 2020, but only formally arrested the following year.
She was deported from China last week after more than three years of incarceration on espionage charges widely seen as politically motivated.
Beijing has also detained a series of people, both Japanese and Chinese, in recent years on allegations of spying for its island neighbour.
In October 2019, Chinese authorities detained a Japanese professor -- reportedly on suspicion of spying -- until he was released and returned to Japan the following month.
And in March 2020, China said it had arrested one of its own citizens reportedly working as a university professor in Japan, claiming he had confessed to spying.
Perennial rivals in East Asia, tensions between China and Japan have long simmered over territorial disputes, Tokyo's colonial history and other flashpoints.
They have flared again since Tokyo this year began releasing contaminated wastewater from the Fukushima nuclear disaster site, a move that international agencies insist is safe but Beijing has lambasted as irresponsible.
