Hong Kong media tycoon Jimmy Lai became the highest-profile person arrested under a new national security law on Monday, detained over suspected collusion with foreign forces as around 200 police searched the offices of his Apple Daily newspaper.

Mainland-born Lai, who was smuggled into Hong Kong on a fishing boat when he was a penniless 12-year-old, has been one of the most prominent democracy activists in the Chinese-ruled city and an ardent critic of Beijing.