Seized items are seen on display at the Hong Kong police headquarters on July 6 after nine Hong Kongers were arrested on terror charges for allegedly trying to manufacture and set off a powerful explosive, police announced. Photo: AFP / Peter Parks

Six secondary school students were among nine Hong Kongers arrested on terror charges for allegedly trying to manufacture a powerful explosive, police announced Tuesday. 

Five males and four females aged between 15 and 39 were arrested Monday on suspicion of “conspiracy to use explosives for terrorist activities,” police said.

“The operation we conducted yesterday was against gangsters [who] tried to manufacture TATP explosive inside a homemade laboratory inside a hostel,” senior superintendent Steve Li, from the city’s new national security unit, told reporters. TATP is a high-powered explosive.

Police said the nine people belonged to a pro-independence group that called itself “Returning Valiant.” 

Those arrested included six teenage students. The three adults worked at a local university, at a secondary school and as a driver.

Li said they were planning to attack public facilities including a cross-harbor tunnel, the railway network, and courtrooms to “maximize damage to society”.

Anti-government sentiment exploded in 2019 during massive and often violent pro-democracy protests that were stamped out with arrests and a new national security law. 

While stability has been widely enforced, Hong Kong remains a deeply polarized city where many residents still seethe under Beijing’s rule.

News of Tuesday’s arrests came just days after a 50-year-old man took his own life after stabbing a police officer in what authorities said was a “lone wolf” attack. 

Police said Tuesday they seized various items from the group, including a small amount of explosives, raw materials to produce TATP, air guns, mobile phones, SIM cards, an operating manual on how to plant bombs and plans for leaving the city.

They also found some HK$90,000 ($11,585) in cash and froze around HK$600,000 in related bank accounts.

Police have made multiple arrests in the last two years for alleged bomb plots although no major attack has been carried out successfully.

In April, a 29-year-old man was jailed for 12-years for manufacturing a kilogram of TATP.