Hong Kong's Apple Daily tabloid responded with defiance on Tuesday to the arrest of owner Jimmy Lai under a new national security law imposed by Beijing, promising to "fight on" in a front-page headline over an image of Lai in handcuffs.

Readers queued from the early hours to get copies of the pro-democracy tabloid a day after police raided its offices and took Lai into detention, the highest-profile arrest so far under the national security law.

"Apple Daily must fight on", the front page headline read, amid fears the national security law amounts to an assault on freedom of speech in the semi-autonomous territory.