Cardinal Joseph Zen in a March 5, 2018 photo. Image Credit: AFP

Hong Kong: China on Thursday defended the arrest of a 90-year-old Catholic cardinal under Hong Kong’s national security law.

Retired cardinal Joseph Zen, one of the most senior Catholic clerics in Asia, was among a group arrested on Wednesday for “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 as he attempted to fly to Europe to take up an academic post.

“The persons concerned are suspected of conspiracy to collude with foreign countries or foreign forces to endanger national security - an act of severe nature,” said the Commissioner’s Office, which represents Beijing’s foreign ministry in Hong Kong.

Criticism came from Western nations who have accused China of eviscerating the freedoms it once promised Hong Kong could maintain.

The United States, which has previously sanctioned key Chinese officials, called on Beijing to “cease targeting Hong Kong’s advocates”.

Canadian foreign minister Melanie Joly called the arrests “deeply troubling”.

EU foreign policy chief Josep Borrell said he was following the arrests with “great concern”.

The Vatican said it was concerned by Zen’s arrest and “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 bishop of the city.

The Hong Kong diocese said on Thursday it was “extremely concerned about the condition and safety of Cardinal Joseph Zen”.

“We trust that in the future we will continue enjoying religious freedom in Hong Kong under the Basic Law,” it said in a statement, referencing the city’s mini-constitution that supposedly guarantees key freedoms.