Police in Hong Kong, where China has been ramping up control, arrested six staffers of a prominent anti-Beijing news outlet on charges of seditious activities.
US Secretary of State Antony Blinken has called on Chinese and Hong Kong authorities to immediately release staff members of the anti-Beijing media outlet Stand News who were arrested after a police raid that shut down the publication.
"We call on PRC and Hong Kong authorities to cease targeting Hong Kong's free and independent media and to immediately release those journalists and media executives who have been unjustly detained and charged," Blinken said in a statement on Wednesday, referring to the People's Republic of China.
"By silencing independent media, PRC and local authorities undermine Hong Kong's credibility and viability," he said.
Hong Kong leader Carrie Lam, however, said on Thursday the raid was aimed at seditious activity not the suppression of the media.
"These actions have nothing to do with so-called suppression of press freedom," Lam told reporters.
"Journalism is not seditious ... but seditious activities could not be condoned under the guise of news reporting."
Police in Hong Kong, where Beijing has been ramping up control, on Wednesday burst into the offices of Stand News, seizing phones, computers and documents and taking away its editor-in-chief.
Stand News later said it was immediately ceasing operations.
Stand News, set up in 2014 as a non-profit organisation, was the most prominent remaining anti-Beijing publication in Hong Kong after a national security investigation this year led to the closure of jailed tycoon Jimmy Lai's Apple Daily tabloid.
The latest arrests were under a British colonial-era law for "conspiracy to publish seditious publication," with police accusing Stand News of articles and blog posts that incited hatred toward the Hong Kong government.
Among those arrested were the editor-in-chief Patrick Lam, and Hong Kong pop star Denise Ho, a board member who resigned in June.
Canadian Foreign Minister Melanie Joly also denounced the arrests including of Ho, who was born in Hong Kong but grew up in Canada.
"We are deeply concerned by the arrests in Hong Kong of current and former board and staff members from Stand News, including Canadian citizen and activist Denise Ho," Joly said.
European Union spokesperson Peter Stano earlier wrote on Twitter that the raid and arrests marked "a further deterioration in #PressFreedom" in the city.
The Society of Professional Journalists, a US group that promotes free expression and ethical standards, voiced solidarity with Stand News.
"SPJ stands with our brave colleagues in Hong Kong who continue to believe in the right of news organisations to be free from government control," said Dan Kubiske, co-chair of the group's international community.
The United States has already imposed sanctions on Hong Kong leaders and curtailed the territory's separate status in US regulations in hopes of changing Beijing's behaviour.