HONG KONG: The arrest of a 90-year-old Catholic cardinal under Hong Kong’s national security law has triggered international outrage and deepened concerns over China’s crackdown on freedoms in the regional financial hub.

Retired cardinal Joseph Zen, one of the most senior Catholic clerics in Asia, was among a group of veteran democracy advocates arrested on Wednesday on a charge of “colluding with foreign forces.”

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.

The four were detained for their involvement in the now-disbanded 612 Humanitarian Relief Fund, which helped pay legal and medical costs for those arrested in the huge and sometimes violent democracy protests that convulsed Hong Kong three years ago.

China responded to the protests with a broad campaign to crush the democracy movement and transform the once-outspoken city into something more closely resembling the authoritarian mainland.

Zen and his colleagues, who were released on bail on Wednesday night, join more than 180 Hong Kong residents arrested under the national security law to date.

Those charged are typically denied bail and can face up to life in prison if convicted.

Criticism came from Western nations that 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 spokesman Karine Jean-Pierre told reporters.

The Vatican said Zen’s arrest concerned them and was “following the development of the situation very closely.”

Cardinal Zen fled Shanghai for Hong Kong after the communists took power in China in 1949 and rose to become the 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 is a long-term advocate of Hong Kong’s democracy movement.

Those arrested on Wednesday were suspected of endangering national security because they allegedly asked foreign nations or overseas organizations to impose sanctions on Hong Kong, police said.