The central government in Beijing imposed the national security law on the semi-autonomous Chinese territory after city leaders were unable to get one passed locally. The move has raised fears that Hong Kong's freedoms and local autonomy are being taken away.
Police did not identify the suspects or their group. An organisation called Studentlocalism — which announced it was disbanding just before the law took effect — said on Facebook that four former members had been arrested on secession charges, including ex-leader Tony Chung.
The police action appeared to target the Initiative Independence Party, which says on its Facebook page that it consists of former Studentlocalism members who have completed their studies and are overseas.
The party, which also posted the news of the arrests, advocates for independence because it believes full democracy for Hong Kong is impossible under Chinese rule, its Facebook page says.
Li said only that the group in question had set up recently and that the posts were made after the law took effect late on June 30.
"They said they want to establish a Hong Kong republic, and that they will unreservedly fight for it," he said. "They also said they want to unite all pro-independence groups in Hong Kong for this purpose."
He warned anyone who thinks they can carry out such crimes online to think twice.
Police have made a handful of other arrests under the new law, all of people taking part in protests and chanting slogans or waving flags deemed to violate the law.
China promised Hong Kong would have its own governing and legal systems under a "one country, two systems" principle until 2047, or 50 years after Britain handed back its former colony in 1997.
China, in justifying the new law, says issues such as separatism are a national security concern and, as such, fall under its purview.
The latest arrests came one day after a leading figure in Hong Kong's political opposition was fired from his university post.
Hong Kong University's council voted 18-2 to oust Benny Tai from his position as an associate law professor, local media reported.
Tai has been out on bail since being sentenced to 16 months in prison in April 2019 as one of nine leaders put on trial for their part in 2014 protests for greater democracy known as the Umbrella Movement.
In a posting on his Facebook account, Tai said he intended to continue writing and lecturing on legal issues and asked for public support.
"If we continue in our persistence, we will definitely see the revival of the rule of law in Hong Kong one day," Tai wrote.
- AP
