The 71-year-old billionaire was arrested on suspicion of collusion with foreign forces, one of the crimes contemplated in the new law that took effect at the end of June, as well as fraud.
China officially welcomed the arrest.
These anti-Chinese agitators in concert with foreign forces have seriously endangered national security. Jimmy Lai is one of their representatives, the Chinese office responsible for monitoring the situation in Hong Kong and Macao said in a statement.
READ ALSO: Hong Kong pro-democracy press mogul Jimmy Lai released on bail
Agnes Chow, for her part, was arrested under the same law, according to a police source.
It is now confirmed that Agnes Chow was arrested on charges of 'incitement to secession' under national security law, which was posted on the Facebook account of the renowned activist.
In total, according to the police source, ten people were arrested this Monday.
They include two of Lai's sons, and Wilson Li, who claims to be a freelance cameraman working for the British television channel ITV News .
Seen by many as Beijing's response to months of pro-democracy demonstrations that rocked the semi-autonomous territory in 2019, the national security law gives authorities new powers to suppress four types of crimes against state security: subversion, separatism, terrorism and collusion with outside forces.
For its part, the EU on Monday denounced the use of this law to stifle freedom of expression.
The US senator of Cuban origin, Republican Marco Rubio, reacted to his inclusion on a black list in Beijing along with ten other senior officials from the North American country.
Last month China put me on the blacklist. Today they sanctioned me, he tweeted. Adding, Jimmy Lai and his son were charged with 'collusion with foreign powers'.