HONG KONG, China—Fourteen people went on trial Monday in Hong Kong for allegedly planning to carry out a bomb attack to murder police officers during pro-democracy protests in 2019, with prosecutors invoking the city's anti-terrorism act.

The defendants, allegedly members of two radical protest groups -- including one called "Dragon Slayers" -- were arrested after police accused them of planning to carry out a bomb attack during a rally marking International Human Rights Day.

Thousands of people have been rounded up and charged over their involvement in months of huge and at times violent protests that kicked off in 2019 calling for greater autonomy from Beijing's rule.

Prosecutor Edward Lau on Monday accused the 14 defendants of plotting to place two bombs along the rally's marching route on December 10 that year to kill police officers.

The prosecution said the protest groups planned to ransack shops to attract authorities. Then-18-year-old member David Su was to push officers closer to the bombs, they said.

"The group planned to take the police guns for their own use after the officers were killed," Lau said.

Ahead of the alleged planned attack -- that did not happen -- police said they found two improvised explosive devices near a secondary school.

They also said they seized four guns including an AR-15 rifle, as well as hundreds of bullets in the home search of three defendants during their investigation.

Since the protests were quashed in 2020, Hong Kong authorities have invoked a variety of legislations -- including reviving a colonial-era sedition charge -- to target activists, pro-democracy politicians, and even ordinary people.

Most significantly, Beijing also imposed a sweeping national security law in mid-2020 to quell dissent.

But the defendants have been charged under the anti-terrorism act, which is the first time the law has been used since it was enacted in 2002.

- Life in prison -

Ten of the 14 defendants are facing two charges that can lead to life in prison -- "bombing of prescribed objects" under the anti-terrorism act and "conspiracy to murder police officers" under Hong Kong's criminal law.

Among the 10, one of them faces an extra anti-terrorism charge of funding the acts, while a woman brought into the case last year is also accused of that. The charge carries a maximum sentence of 14 years in jail.

Eight of the defendants are also charged with various offences relating to possession and manufacturing of explosives, firearms and ammunition, some of which carry a maximum sentence of life in prison.

Other than the woman admitted late in the trial, all of the accused have been kept behind bars for more than two years.

Eight defendants pleaded guilty on Monday, and the trial is expected to last more than two months.

By the end of 2023, more than 11,200 people had been arrested and nearly 3,000 charged over their participation in the 2019 protests.

The Hong Kong government announced last month its plan to create another national security law to cover more offences, including treason and espionage.