Hong Kong publisher turned democracy activist Jimmy Lai received a one-year jail sentence Friday for participating in an unauthorized assembly in August 2019 - joining four other former politicians who were also jailed.

Democratic Party founder and the city's "father of democracy" Martin Lee Chu-ming, 82, was given an 11 month suspended sentence.

This is the first criminal conviction of Lai, 73, but not his last. He is currently in jail awaiting trial for alleged national security law violations.

The pair, alongside six other Hong Kong opposition figures, were accused of encouraging an illegal rally at Victoria Park Aug. 18 and then leading some 300,000 people on an unauthorized march to Central that blocked roads and caused traffic disturbances.

"Having arrested the majority of Hong Kong's most prominent dissidents...the authorities are now mopping up remaining peaceful critics under the pretext of bogus charges related to the 2019 protests," Amnesty International APAC regional director Yamini Mishra said.

On Friday, West Kowloon District Judge Amanda Woodcock handed all eight activists between eight- and 18-month jail sentences.

Former politicians Albert Ho and Margaret Ng received one-year jail terms, suspended for two years, while union leader Lee Cheuk-yan was jailed for one year.

Politician Leung Kwok-hung received the longest sentence and will serve 18 months in prison.

The protest and resulting march was "a direct challenge to the police," the judge said in her ruling. "All defendants were well known, which would guarantee to draw crowds and followers. They made a conscious decision to break the law during a volatile time."

People who participate in or organize rallies without prior police approval are liable to spend up to five years behind bars under the Public Order Ordinance.

Judge Woodcock will hear cases against Lai and two former lawmakers Friday afternoon for their participation in another illegal protest Aug. 31, 2019.