Five men accused of making explosives before a contentious vote on political reform in 2015 appeared in a Hong Kong court Tuesday in a case that triggered concern about the radicalisation of protesters.

The men were arrested at a time of heightened political tensions in Hong Kong, following the failure of mass “Umbrella Movement” rallies to win democratic reform for the semi-autonomous city in protests that were an unprecedented rebuke to China.

The abandoned ATV studios. Photo: Tom Grundy/HKFP.

The five were detained as legislators prepared to vote on a Beijing-backed reform bill on how the city should choose its next leader. The legislation was eventually voted down by pro-democracy lawmakers because it stipulated that candidates must be vetted by a committee loyal to Beijing.

The court heard Tuesday how one of the five accused had joined an anti-government group which had discussed causing “chaos” around the vote.

Local media have previously reported that the group advocated independence for Hong Kong.

Calls for self-determination or even a full split from China grew out of the Umbrella Movement’s failure to win concessions through largely peaceful protests.

The five men, in their twenties and thirties, have been charged with conspiracy to make explosives and three of them are also charged with possessing explosives.

At the first full day of the trial, the prosecution said they had tried to make explosives at an abandoned graffiti-covered television studio in the northeastern district of Sai Kung.

Police had seen flashes and smoke coming out of the building and during a raid had discovered acid, hydrogen peroxide and acetone, prosecutor Jonathan Man Tak-ho told the jury.

Police from the Explosive Ordnance Disposal Bureau wearing explosive protection gear.

“The mixture of these three things can produce TATP (a powerful explosive),” said Man.

One of the defendants admitted being part of an anti-establishment group, Man told the court.

“He had been invited to join an anti-government organisation called the National Independent Party” and he did join and meet with members, said Man, citing a recorded interview with police.

Its members “discussed creating chaos before or after voting”, Man told the court, referring to the parliamentary vote on the reform package.

Police also found goggles, gloves, electronic scales, laptops containing formulas and browsing histories related to mixing chemicals for explosives, Man said.

The defence has not yet delivered its arguments.

The suspects, if convicted, could face up to 20 years in prison for conspiring to manufacture explosives.

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