Jackie Chen, 48, belonged to a group of social workers who tried to mediate between protesters and riot police during tense standoffs in 2019, when Hong Kong saw huge and sometimes violent demonstrations.

Chen -- who was acquitted in 2020 but convicted after prosecutors sought a retrial -- was handed a prison term of three years and nine months.

Deputy district judge May Chung said Chen and three others were arrested at an "extremely serious" riot in August 2019 involving street barricades and objects set on fire, which could have resulted in "unimaginable losses".

The judge earlier ruled that Chen's verbal support for the protesters, delivered via a loudhailer, "bolstered their determination and confidence to resist the police".

Chen's sentence was partly reduced because of the mental stress caused by the retrial and for her prior contributions as a social worker.

The other three people, who had pleaded guilty, were jailed for two years and five months.

Those found guilty of the riot offence at the district court face a maximum prison term of seven years.

Hong Kong authorities have prosecuted thousands in relation to the 2019 protests, including many young people who put their studies or careers on hold due to slow-moving court proceedings.

A judiciary representative said this week that 96 percent of the nearly 2,400 protest-related cases had been cleared as of last year.

More than 200 of the approximately 230 cases involving national security have also been cleared, the representative added.

Beijing imposed a sweeping national security law on Hong Kong in 2020 to quell dissent.

The city passed a separate, home-grown security law known as Article 23 last year.

Under that law, a man was jailed for 12 months on Tuesday after he pleaded guilty to publishing seditious content on social media.

Chow Kim-ho, 57, posted on platforms like Facebook "with the main theme of overthrowing the Chinese Communist Party regime" and called for Taiwan independence, according to the magistrate.