Jimmy Lai is a well-known representative of the democracy movement and owns the magazines Apple Daily and Next Magazine, which are both pro-democracy and Beijing-critical. He has been arrested on suspicion of collaborating with foreign powers, police sources for the news agency AFP confirm.

Hong Kong police say seven people between the ages of 39 and 72 have been arrested on suspicion of violating the new law, and they do not rule out that more arrests may be made.

Hours after the arrest, a handcuffed Lai was taken through Apple Daily's editorial office while hundreds of police searched and seized journalists' documents, reports The Guardian.

"The day when freedom of the press officially died"

Journalists in Hong Kong have repeatedly warned that the security law will affect press freedom in Hong Kong. Chris Yeung, head of the Hong Kong Journalists' Union, said the raid was "terrible".

"I think there has been this kind of repression of press freedom in some third world countries, but I never expected it to happen in Hong Kong," he told The Guardian.

Keith Richburg, correspondent and head of Hong Kong University's media school, says the arrest of Lai and the raids on Apple Daily's editorial office are scandalous.

- It is the day when the freedom of the press officially died, and it is not a natural death. It was killed by Beijing and Carrie Lam and Hong Kong police, he told The Guardian.

Tilde Lewin, foreign reporter at Sweden Television, agrees that the arrest of Jimmy Lai poses a serious threat to press freedom in Hong Kong.

- It will change what you dare to print in Hong Kong, she says.

See the interview with Tilde Lewin in the clip above.