Hong Kong pro-democracy media mogul Jimmy Lai was charged Friday with violating the national security law, as authorities intensify efforts to suppress dissent after a period of social unrest in the former British colony.

Lai, the founder of Next Digital Ltd. which publishes the outspoken Apple Daily newspaper, was arrested in August on suspicion of colluding with foreign forces, a crime punishable by life imprisonment.

Lai was indicted along with two associates last week on a charge of fraud over a land-use violation involving his media office, and has been remanded in custody after a magistrate denied him bail.

Police said in a statement on Friday that he was also charged with the additional offense of "collusion with a foreign country or with external elements to endanger national security" and will appear in court for mention on Saturday.

The Apple Daily quoted sources as saying that Lai is alleged to have called for foreign sanctions against Hong Kong and its officials through Twitter and in interviews with foreign media in recent months.

In July last year, Lai met with senior U.S. officials such as Secretary of State Mike Pompeo and Vice President Mike Pence in Washington to discuss a controversial bill that would have allowed the extradition of criminal suspects to mainland China.

The bill was later withdrawn amid widespread protests among Hong Kong people that morphed into a months-long, sometimes violent anti-government movement.

China's official Xinhua News Agency has called Lai "an instigator of Hong Kong riots."

Lai was arrested in August along with his two sons and four associates. Some 200 police officers also raided the daily's headquarters.

The national security law -- enacted by the National People's Congress Standing Committee and imposed on Hong Kong on June 30 -- outlaws acts of secession, subversion, terrorism and collusion with foreign forces.

While at least four people have been charged with violating the law, Lai is the first to be indicted over alleged collusion with foreign forces.

As of Monday, a total of 40 people had been arrested for allegedly breaching the law, according to police.

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