Four young Hong Kong activists have been arrested for allegedly organizing and inciting secession, the police said late Wednesday.

The three males and one female, all students aged between 16 and 21, were members of an organization that openly advocated for the independence of Hong Kong and incited others to join the same cause by posting messages on social media, the force's national security department said.

The organization has declared it aims "to establish a Hong Kong Republic, to fight for Hong Kong's independence by any means and unite all interested parties to join force in doing so," Li Kwai-wah, a senior officer of the newly established department, told reporters.

Although not a first, the high-profile arrests came less than a month after China imposed a sweeping anti-subversion law in the territory on June 30. A man who allegedly rode a motorcycle into a group of police officers during a July 1 demonstration while carrying a flag whose slogans are considered a breach of national safety was also charged under the law.

The four were arrested for allegedly breaching articles 20 and 21 of the National Security Law, which cover acts of organizing, planning or participating in secession and of inciting others.

"Even (had) the acts of crime taken place on foreign soil, we would still have jurisdiction over the case, as stipulated in the law," Li said, adding that it was Hong Kong police who made the arrests without the involvement of any other agencies.

China set up a national security office in Hong Kong following the law's imposition to handle selected cases in which suspects could be transferred to mainland China for prosecution.

A pro-independence group called Studentlocalism said on its Facebook page that four former members, including convener Tony Chung, have been arrested and will remain in police custody.

The group announced on June 30, the day the law took effect in Hong Kong, that its Hong Kong chapter had been disbanded in the face of the new law while its foreign branches in Taiwan, the United States and Australia would carry on advocating for Hong Kong independence, "until Hong Kong becomes an independent sovereign state."

The national security law targets activities that China defines as acts of secession, subversion, terrorism or collusion with foreign forces.

The maximum penalty is life imprisonment.