The Vatican has expressed concern over the arrest of a retired cleric, Cardinal Joseph Zen, in Hong Kong.
"The Holy See has learnt the news of Cardinal Zen's arrest with concern and is following the development of the situation very closely", the Vatican said in a brief statement.
Zen, 90, is a former bishop of Hong Kong and one of the most senior Catholic clerics in the Chinese business hub.
He was one of a group of veteran democracy advocates who were arrested under Hong Kong's national security law, legal and police sources said Wednesday. He was later released on bail
Zen has been critical of the Vatican's decision to reach a compromise with China over the appointment of bishops on the mainland.
Those arrested were all trustees of a now-disbanded fund that helped finance demonstrators detained during massive democracy protests that swept Hong Kong three years ago.
Cantonese pop singer Denise Ho, veteran barrister Margaret Ng and prominent cultural studies scholar Hui Po-keung were also arrested, the latter at the airport as he attempted to travel to Europe to take up an academic post.
China had responded to the democracy protests with a broad campaign to crush the movement and transform the once outspoken city into something more closely resembling the authoritarian mainland.
Zen and his colleagues, join more than 180 Hong Kongers arrested under the national security law to date.
- 'Deeply troubling' -
Criticism came from Western nations who have accused China of eviscerating freedoms it once promised Hong Kong could maintain.
The United States, which has previously sanctioned key Chinese officials over the ongoing crackdown, called on Beijing to "cease targeting Hong Kong's advocates".
"Freedom of expression (is) critical to prosperous and secure societies," White House spokesperson Karine Jean-Pierre told reporters.
Canada, meanwhile, said consular officials were trying to access Ho, a popular singer and LGTBQ campaigner who is a dual Hong Kong-Canadian national.
Canadian foreign minister Melanie Joly called the arrests "deeply troubling".
"The ongoing targeting of civil society groups erodes the rights and freedoms of Hong Kong residents guaranteed under Hong Kong’s Basic Law," she wrote on Twitter.
EU foreign policy chief Josep Borrell said he was following the arrests with "great concern".
Human Rights Watch called it a "shocking new low for Hong Kong".
"Even by Hong Kong’s recent standards of worsening repression, these arrests represent a shocking escalation," added Amnesty International.
- 'Six crimes' -
Cardinal Zen fled Shanghai for Hong Kong after the communists took power in China in 1949 and rose to become bishop of Hong Kong.
He has been critical of the Vatican's decision to reach a compromise with China over the appointment of bishops on the mainland and a long-term advocate of Hong Kong's democracy movement.
Those arrested Wednesday were suspected of endangering national security because they allegedly asked foreign nations or overseas organisations to impose sanctions on Hong Kong, police said.
Ta Kung Pao, a nationalist newspaper that answers to Beijing's Liaison Office in Hong Kong, published an article Thursday detailing "six crimes" allegedly committed by the group and their defence fund.
The alleged crimes included funding lobbying trips and activist meetings with British lawmakers, providing financial aid to Hong Kong "rioters" who had fled to Canada and Taiwan, and accepting donations from overseas.
It also listed a HK$1.3 million ($165,000) donation from Apple Daily, a popular pro-democracy tabloid that collapsed last year after its assets were frozen by the security law.
But most of the alleged actions cited by Ta Kung Pao took place before the enactment of the national security law, which is not supposed to be retroactive.
Reporting in the paper and its sister publication Wen Wei Po often heralds action by Hong Kong's national security police, and the defence fund has previously been a target of coverage.
The fund disbanded last year after national security police demanded it hand over operational details including information about its donors and beneficiaries.