Dong, a senior columnist at the Communist Party newspaper Guangming Daily, was detained in February 2022 along with a Japanese diplomat at a Beijing restaurant.

The diplomat was released after a few hours of questioning, but Dong, 62, was charged with spying last year.

"The Beijing No. 2 Intermediate People's Court convicted Yuyu of espionage, a crime that requires that the prosecution prove that the defendant knowingly acted on behalf of 'espionage organisations' and their agents," according to a statement shared by his family with AFP.

According to the judgement, the Japanese diplomats Dong met with, including then-ambassador Hideo Tarumi and current Shanghai-based chief diplomat Masaru Okada, were named as agents of an "espionage organisation", the family statement added.

"We are shocked that the Chinese authorities would blatantly deem a foreign embassy as an 'espionage organisation' and accuse the former Japanese ambassador and his fellow diplomats of being spies," Dong's family said.

On Friday, Beijing's foreign ministry spokeswoman Mao Ning responded to Dong's case by saying "China is a country ruled by law".

The Japanese embassy told AFP that it would not comment directly on the case.

But an embassy spokesperson told AFP in an email: "The diplomatic activities of Japanese diplomatic missions abroad are carried out in a legitimate manner."

In Washington, State Department Spokesman Matthew Miller condemned Dong's jailing and called for his immediate release.

"His arrest and today's sentencing highlight the PRC's failure to live up to its commitments under international law and its own constitutional guarantees to all its citizens, which include the right to freedom of speech and freedom of the press," Miller said in a statement referring to China by its official name, the People's Republic of China.

The Committee to Protect Journalists (CPJ) condemned the "unjust verdict" and called for Dong's immediate release.

"Interacting with diplomats is part of a journalist's job," the NGO's Asia program coordinator Beh Lih Yi said in an email to AFP.

"This sentencing cements China's position as the world's leading jailer of journalists," added Yi.

Under Chinese law, a person convicted of espionage can be jailed for three to 10 years for less severe cases or receive heavy punishment, including life imprisonment, for serious cases.

Dong's work has been published in the Chinese editions of The New York Times and the Financial Times.

He won the prestigious Nieman Fellowship at Harvard University in 2006-2007.

He was also a visiting fellow at Keio University in Japan in 2010 and a visiting professor at Hokkaido University in 2014.

Civil liberties and freedom of expression have dramatically receded in China under President Xi Jinping's decade-long tenure.

The Communist Party maintains tight restrictions on domestic media outlets, and Chinese nationals who work with foreign outlets are routinely harassed.

China is the worst country for jailing media workers with 44 journalists behind bars as of December last year, according to a CPJ ranking.

In February, a Beijing court handed a suspended death sentence to jailed dissident writer Yang Hengjun after finding the dual Chinese-Australian citizen guilty on espionage charges.

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THE NEW YORK TIMES COMPANY