Former Bishop of Hong Kong, Cardinal Joseph Zen, says there is no freedom of expression in the city anymore after Beijing imposed a national security law earlier this year.

In comments to Reuters, the 88-year-old said Hong Kong was "becoming like any other city in China."

"We are at the bottom of the pit – there is no freedom of expression anymore," he told the news agency. "All these things are normal in mainland China."

The cardinal added that he fears the territory's Catholic authorities are seeking to maintain neutrality towards the government.

"I'm afraid that a real persecution has already begun," he said. 

While Zen has been consistently outspoken against Beijing, his successor Cardinal John Tong has been more placatory in his approach.

After the passing of the national security law, Cardinal Tong sent a letter to clergy asking them to refrain from "instigating hatred and social disorder", and to "keep abreast of the times and speak out for justice, and, on the other hand, avoid using slandering and abusive expressions that insinuate or instigate hatred and social disorder, inasmuch as they are against the Christian faith."

His comments are in stark contrast to those of Cardinal Zen, who said he was prepared to be arrested.

"I shall be prudent; I do not seek to offend, but when I deem it necessary, I will say it," he said.

"If such right and proper words are considered to be against their law, I will endure all the suing, trials and arrests. Numerous predecessors have endured similarly. We have seen how God has always helped them."

Christian pro-democracy leader Joshua Wong was imprisoned earlier this month over his involvement in Hong Kong protests throughout last year.

He told German newspaper Die Welt that he was leaning on Romans 5:3-4.