Chief executive of the Confederation of Trade Unions, Mung Siu-tat, said the three films - "Inside the Red Brick Wall", "Eternal Springs in the Mountains" and "Taking Back the Legislature" are not banned in Hong Kong, with the films only being classified as Category III under the city’s three-tier film classification system.

Films classified as Category III are for persons aged 18 or above only, with the age restriction strictly enforced under the Hong Kong Film Censorship Ordinance (Cap. 392).

“The documentaries only revealed Hong Kong’s social issues, and are completely legal for eligible persons to watch,” said Mung.

He also slammed those who “made a big fuss” were being critical like being in a "struggle session during the cultural revolution.”

"They have been launching a cultural revolution to criticize people holding different political opinions. I think that's very worrying. The freedoms we still enjoy are being eroded," he said.

Earlier today, Chow said the group could be seen as "promoting terrorism" for screening the documentaries. He also called for the authorities to take action against the group.

"Events to incite serious violence, riots or causing subversion are all prohibited if you read articles 24 to 27 of the national security law. I think ... these people who organized these events might be against the law and I urge the police to take swift law enforcement action," he said.

The three films focus on the police siege of Polytechnic University, clashes at Chinese University, and the storming of Legco.