After multiple media reports, Wells Fargo confirmed last week that it was providing assistance to the Atlanta-based Mao, who entered China in recent weeks but is now unable to leave.

Chinese foreign ministry spokesman Guo Jiakun said on Monday that Mao was "involved in a criminal case currently being investigated by the Chinese authorities".

"The Chinese law enforcement agencies have imposed exit restrictions in accordance with the law," Guo said.

He did not give details of Mao's alleged offences, and Wells Fargo has not provided more information on her case.

But the San Francisco-based bank is now restricting its employees from visiting China following this case, according to reports.

It said in a statement to AFP on Friday that it was "closely tracking this situation and working through the appropriate channels so our employee can return to the United States as soon as possible".

Wells Fargo declined to comment on China's foreign ministry saying that Mao was involved in a criminal case, when contacted by AFP.

Guo said Mao "cannot leave the country while the case is ongoing, and has an obligation to cooperate with the work of investigators".

He stressed that it was an "individual case" and that China would "continue as ever to welcome people from every country to travel and do business here".

"No matter whether you are Chinese or not, you must follow Chinese laws while in China," he said.

- Tensions and detentions -

Industry groups say multinational firms have faced an increasingly difficult business environment in recent years, citing a lack of transparency on data laws and prolonged detentions of employees in the country.

The trend has coincided with growing tensions between Beijing and certain Western nations, particularly the United States but also regional competitors.

The Washington Post reported on Sunday, citing four unnamed sources, that an employee at the US Commerce Department was being prevented from leaving China after failing to declare on his visa application that he worked for the American government.

The unnamed Chinese American man, who works for the Patent and Trademark Office, had travelled to China several months ago to visit family, the newspaper reported.

Asked about the report on Monday, Guo said he was not familiar with the case.

On Wednesday, a Chinese court sentenced a Japanese businessman from pharmaceutical company Astellas to three and a half years in prison for spying.

Another pharma giant, UK-headquartered AstraZeneca, said in November that the head of its China operations, Leon Wang, had been detained, after reports that the firm was under investigation for potentially illegal data collection and drug imports.

And in 2023, a senior executive at US risk advisory firm Kroll was prohibited from leaving China, according to the Wall Street Journal.

mjw-ll-mya/rsc

WELLS FARGO & COMPANY

ASTELLAS PHARMA

ASTRAZENECA