A pro-democracy Hong Kong radio DJ was convicted of seditious speech on Wednesday under a British colonial-era law that authorities have embraced as China flattens dissent in the business hub.

Tam Tak-chi, 49, is among a growing number of activists charged with sedition, a previously little-used law that prosecutors have dusted off in the wake of massive and sometimes violent pro-democracy protests in 2019.

Tam's trial was the first since Hong Kong's 1997 handover in which a sedition defendant fought his case by pleading not guilty and went through a full trial.

Two previous recent prosecutions were wrapped up after guilty pleas.

As a result, Tam's conviction is a legal watershed because it sets precedents for a host of upcoming sedition prosecutions as China remolds Hong Kong in its own authoritarian image.

Better known by his moniker "Fast Beat," Tak hosted a popular online talk show that backed democracy and was highly critical of the government, often using colorful language.

He was a regular presence at protests and often set up street booths to deliver political speeches.

Prosecutors focused on the street booths, with Tam convicted on seven counts of "uttering seditious words" as well as other charges such as disorderly conduct and disobeying a police officer.

Authorities said Tam incited hatred against the authorities by chanting the popular protest slogan "Liberate Hong Kong, Revolution of Our Times" 171 times, cursing the police force some 120 times, and repeatedly shouting "Down with the Communist Party.”

"The attack on the Communist Party is only part of the seditious words uttered by the accused," district judge Stanley Chan said in his verdict.

"Looking at what he (Tam) said, it's far beyond criticizing and theorizing," he added.

Sedition is separate from the sweeping national security law that Beijing imposed on Hong Kong in 2020.

But the courts treat it with the same severity and there are plans to make sedition one of a number of new national security crimes later this year, meaning it will soon carry a much longer jail term.

Tam was arrested in September 2020 and denied bail, as happens in most national security cases.

His trial began in July 2021 but was delayed for a landmark High Court ruling in which judges declared the popular protest slogan "Liberate Hong Kong" was secessionist and therefore illegal under the new security law.

That ruling legally crystallized the reality that certain views and slogans are now forbidden in Hong Kong under the security law.

In Hong Kong, sedition is broadly defined as any words that generate "hatred, contempt or disaffection" towards the government or "encourage disaffection" among residents.

It carries up to two years in jail for a first offense.

First penned by colonial ruler Britain in 1938, it was long criticized as an anti-free speech law, including by many of the pro-Beijing local newspapers now praising its use.

By the time of the 1997 handover, it had not been used for decades but remained on the books.

On the same day Tam was convicted, police charged two men aged 17 and 19 with "uttering seditious words" in a separate case concerning a campus protest in 2020.

In recent months, sedition charges have been brought against pro-democracy unionists who produced euphemistic children's books about a village of sheep defending itself from wolves; journalists from now-shuttered pro-democracy news outlets; and a former pop star turned democracy activist.

In January, a man was jailed for eight months and a woman 13-and-a-half months after pleading guilty in two separate cases over seditious leaflets.