The 25-year-old woman, an employee of the Office of the Government Chief Information Officer was arrested in Heng Fa Chuen on Thursday on suspicion of crimes including conspiring or soliciting murder on an online forum, as well as encouraging unauthorised assemblies.

Officers from the Cybersecurity and Technology Crime Bureau believe she posted messages in an online forum encouraging the murder of off-duty police and knife attacks on officers, as well as encouraging people to join an unauthorised protest in Kowloon on Sunday.

"In addition, she may have also violated the interim injunction order of the High Court prohibiting the promotion, encouragement and incitement of the use or threat of violence through the internet," Superintendent Wilson Tam from the bureau said on Friday.

"I would like to remind the public that the interim injunction order is still effective, and any person who violates the order may be liable to an offence of contempt of court."

Police say they will consult the Department of Justice before deciding on charges for the suspect.