HONG KONG (REUTERS) - Hong Kong's national security police on Wednesday (May 11) arrested Cardinal Joseph Zen, one of the most senior Catholic clerics in Asia, and four others who helped run a now-disbanded humanitarian fund for protesters, media reported.

One legal source familiar with the matter told Reuters that five people had been arrested including Zen, 90; senior barrister Margaret Ng, 74; activist and pop singer Denise Ho; former lawmaker Cyd Ho; and former academic Hui Po-keung.

Zen has long been an advocate of democratic causes in Hong Kong and China, and has spoken out against what he viewed as China's growing authoritarianism under President Xi Jinping.

Hui had already been arrested at the airport on Tuesday night for alleged "collusion with foreign forces" according to media reports, while Ho is already in prison for a separate case.

Zen and the others faced the same charge, media said.

The five were trustees of the "612 Humanitarian Relief Fund" which helped protesters who had been arrested during pro-democracy, anti-government protests in 2019 to help pay their legal and medical fees.

The Hong Kong Catholic Diocese, Vatican and the Hong Kong police gave no immediate comment.

The fund was scrapped last year after the disbandment of a company that had helped receive donations through a bank account.

The arrests come after police said last September that they had started investigating the fund for alleged violations of the national security law.

Hui, an associate cultural studies professor at Lingnan University, had once taught exiled activist Nathan Law.

"If you want to punish someone, you can always find an excuse," Law wrote on his Facebook page in response to Hui's arrest.

Beijing imposed the sweeping national security law in June 2020 that punishes terrorism, collusion with foreign forces, subversion and secession with possible life imprisonment.

Critics, including the United States, say the law erodes the freedoms promised by China under the "one country, two systems" arrangement when Hong Kong was returned from British to Chinese rule in 1997.

Hong Kong authorities, however, say the law has brought stability to the city after the 2019 mass demonstrations.