Pong Yat-ming and three employees of Book Punch face allegations of selling seditious publications under Hong Kong's 2024 national security law, local newspapers South China Morning Post and Ming Pao and broadcaster TVB reported Tuesday, citing unnamed sources.

Officers searched the bookshop and seized various materials, including a biography of Lai, who was sentenced last month to 20 years in prison for national security crimes.

Human Rights Watch warned on Wednesday that "Hong Kong has become increasingly dystopian".

"First, the authorities jailed the newspaper publisher, then they arrested the person selling books about him. Who's next?" Elaine Pearson, HRW's Asia director, said in a statement.

"It will be the ordinary people who suffer the consequences over time," she added.

Asked by AFP about the bookstore arrests, police only said that they "take actions according to actual circumstances and in accordance with the law".

An AFP reporter saw Book Punch was shut on Tuesday, with a notice that read: "Due to an unexpected incident, closed for one day, sorry for the inconvenience".

Lai's biography, "The Troublemaker", is authored by Mark Clifford, a former director of the 78-year-old mogul's company, Next Digital.

It chronicles Lai's immigration from mainland China to Hong Kong, where he became a billionaire dissident and founder of the now-shuttered tabloid Apple Daily.

Urania Chiu, a law lecturer at Oxford Brookes University, called the reported Book Punch case a "highly concerning development".

"Given the broad and malleable definition of seditious intention, it is hard to say that anyone can have certainty about what is and is not seditious," Chiu told AFP.

Hong Kong passed a homegrown national security law in 2024, which came in addition to a broader law imposed by Beijing after democracy protests seized the financial hub in 2019.

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