National security police on Monday said they arrested one more person on suspicion of "offences in connection with seditious intention" under the Basic Law Article 23 national security legislation.

Police said seven people, including the former vice-chairwoman of the now-defunct Hong Kong Alliance, Chow Hang-tung, were arrested last week in connection with seditious posts published on social media ahead of what officials described as a "sensitive date".

Chow continues to be remanded at Tai Lam Centre for Women. The other six have been released on bail, with police accusing one of them of funding fugitive Nathan Law and other individuals through an online subscription platform.

It's understood that a 62-year-old man arrested in Sha Tin on Monday is Chow's uncle.

He's detained for further investigation.