A source also confirmed that Chiu, whose seven-year sentence was due to end in early 2028, left prison on Tuesday after being granted release for good behaviour.

His release two years ahead of his original sentence makes him the first national security convict to secure remission from the Correctional Services Department.

The former district councillor was one of the organisers of an unofficial poll, which the court ruled last year was part of a plot to overthrow the government in 2020.

A total of 45 former politicians and activists were convicted for their role in a conspiracy to subvert state power under the Beijing-decreed national security law, while two others were acquitted.

Chiu was jailed for seven years after the court reduced his sentence due to his guilty plea and the help he rendered to prosecutors by testifying against 16 of their former comrades who pleaded not guilty in a 118-day trial.