Six secondary school pupils and a teacher are among nine people arrested over an alleged bomb plot in Hong Kong.

The pupils were trying to make an explosive called triacetone triperoxide (TATP) in a homemade laboratory in a hostel, police said.

They allegedly planned to use the substance to bomb court rooms, cross-harbour tunnels and railways.

And police said they also intended to put TATP in rubbish bins on city streets to “maximise damage caused to society”.

The students are said to have been deliberately recruited by group Returning Valiant, which had rented the hostel room in the busy shopping district of Tsim Sha Tsui for about a month.

The nine suspects arrested – five men and four women – are aged between 15 and 39, Hong Kong Police National Security Department senior superintendent Li Kwai-wah said.

A university management-level worker and an unemployed person are also among the nine people detained on suspicion of terrorist activities.

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Police said they have seized equipment and materials used to make TATP as well as a “trace amount” of the explosive.

Officers have also frozen about 600,000 Hong Kong dollars – equivalent to £55,000 – in assets which they believe could be linked to the plot.

TATP has been used across the globe in terror attacks including in London and Israel.

Senior Superintendent Steve Li told reporters: “They had a good division of labour among those arrested.

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“Some of them provided money. Some are the scientists – the ones who made the TATP in the room.

“One is responsible for the sourcing of chemicals and other materials needed for the plan, while another small group of people create the bombs, using chemical equipment.

“There is also a surveying team and an action team, which is responsible for laying the bombs.”

The arrests follow months of anti-government protests in Hong Kong.

Beijing imposed a national security law last year, with those found guilty of crimes including terrorism and collusion with foreign forces facing life behind bars.

Authorities insist the law has “restored stability”.

But critics – including Western governments, lawyers and international human rights groups – say the law is being used to crush dissent in the former British colony.

The Hong Kong government said that while freedoms in the global financial hub must be respected, they are not absolute and cannot endanger the security law.