"Jimmy Lai has been arrested for collaborating with foreign powers," Mark Simon of Lai's media company Next Digital wrote on Twitter.

A police source confirms the information to AFP, and Hong Kong police state according to Reuters that they have arrested seven people in the age range 39-72 years, suspected of violating the new law, and do not rule out that more arrests may be relevant.

Lai, who is 72 years old, is a prominent figure in the democracy movement. He owns the Apple Daily and Next Magazine, both of which are pro-democracy and Beijing-critical.

Has been arrested before

He was arrested earlier this year on charges of illegal assembly, along with other leading activists, as a result of protests in Hong Kong last year.

Jimmy Lai is the highest-ranking person who has so far been detained as a result of the new legislation.

- I'm ready for jail. If that happens, I'll have the opportunity to read books I have not read. The only thing I can do is continue to be positive, he said in an interview with the news agency AFP in June, a couple of weeks before the new law came into force.