Hong Kong media tycoon Jimmy Lai has been arrested under the city's new national security law.

Lai — the founder of Apple Daily — is believed to have been arrested on Aug. 10 on suspicion of collusion with a foreign country, uttering seditious words, and conspiracy to defraud, reported South China Morning Post.

SCMP sources said the 72-year-old had been detained by officers from the new police unit set up to enforce the security law.

They appeared at Lai’s residence shortly after daybreak.

The New York Times reported that Lai's two sons were also arrested, suggesting that Lai's private investments are similarly under investigation as neither son is affiliated with Apple Daily.

Apple Daily livestreams as police search building

Meanwhile, Apple Daily published a livestream on its Facebook page of police officers searching its office.

Nearly 200 police officers conducted the search, according to Apple Daily.

Apple Daily said that while the police claimed to have a warrant for the search, no warrant was produced for reporters to see.

Lai is part of the third set of arrests since the law took effect on June 30.

According to the BBC, Hong Kong police have said that seven people were arrested on Monday for breaching the national security law.

However, they have not confirmed if Lai is among them.

Frequent critics of Beijing

Estimated to be worth upwards of US$1 billion (S$1.37 billion), Lai and Apple Daily have been frequent critics of Hong Kong and Beijing.

According to The New York Times, during the 2019's pro-democracy protests, a weekly column was published in Apple Daily wherein Lai cheered on the demonstrators.

He was also critical of the national security law, telling the BBC that it was a "death knell for Hong Kong".

Lai elaborated that it would see Hong Kong lose the rule of law and become as corrupt as mainland China.

Speaking to AFP two weeks before the law came into effect, Lai said that he was prepared for prison.

"If it comes, I will have the opportunity to read books I haven’t read. The only thing I can do is to be positive.”

"The establishment hates my guts," he said in a 2019 interview with The New York Times.

"They think I’m a troublemaker."

Top image screenshot from Apple Daily's Facebook page