Police say four Hong Kong tertiary students were among six men arrested on Monday in connection with a blast outside the Legislative Council building in Admiralty earlier this month.
One of the four students was believed to be the person behind the dustbin blast plot on December 9. Another was a former part-time policeman-turned-Occupy movement protester last year, Joe Yeung Yat-long, 22. He is a student at Shue Yan University.
After making five arrests early on Monday morning, officers detained a worker from the Macau ferry terminal as he returned to Hong Kong. A police source said he was accused of buying alcohol and newspaper in the arson case.
All six men were being held for questioning but none had been charged.
Initial investigations showed two of the six suspects, aged between 18 and 24, were members of Valiant Frontier, a radical pro-Hong Kong independence group. It had rallied online against the controversial copyright bill, which it claimed was an attempt by the government to restrict Hong Kong's freedom of speech.
Superintendent Ng Wai-hon of Hong Kong Island regional crime unit said: "This group of people is organised and had a premeditated plan [to commit a crime]. They broke a fire alarm and then used igniting objects to set alight a rubbish bin causing a blast."
Lawmaker Cyd Ho Sau-lan, of the opposition Labour Party, was pleased with the police's swift action but said: "It is unfair for the police to label the suspects as members of localist groups, as if all people from localist groups are bad guys."