Six people were arrested on Tuesday under Basic Law Article 23 national security legislation, with police saying the group is suspected of "offences in connection with seditious intention".

National security police accused a woman who was on remand of taking advantage of "a forthcoming sensitive date" and publishing seditious posts on social media anonymously, with the help of five others.

Secretary for Security Chris Tang said former vice-chairwoman of the now-defunct Hong Kong Alliance, Chow Hang-tung, was one of those arrested.

The suspects, aged between 37 and 65, were arrested by national security police at various locations in the city, including the Tai Lam Centre for Women.

Social media posts since April were allegedly aimed at inciting public hatred of the central government, the SAR administration and the judiciary, and were allegedly designed to encourage people to organise or take part in illegal activities, police said.

Electronic devices suspected of having been used to publish posts with seditious intention were among items seized during the operation, the force added.

These are the first arrests made under Hong Kong's homegrown national security legislation that came into effect in March.

A police spokesperson noted that people found guilty of committing offences in connection with seditious intention face a maximum penalty of seven years in prison.

The spokesperson also warned that people who try to endanger national security should not think they can avoid police investigation by making anonymous comments online.

“The allegations (against) this group of people are using a Facebook page on social media to advocate hatred against our central government, the Hong Kong government and also our judiciary,” Tang told reporters.

“They're relating to a forthcoming sensitive date. But I would like to reiterate that... the main crime is not about the subject. It's about their utilising the subject during which they incited hatred against the central government and our Hong Kong government and the judiciary. This incitement of hatred is the cause of the crime.”