Police National Security Department arrested nine people who are suspected of engaging in terrorist activities, contravening Article 24 of the National Security Law.

The five males and four females were arrested yesterday, aged between 15 and 39, including six secondary school students.

The department's Senior Superintendent Li Kwai-wah said at a press conference today that the arrestees are members of an organisation which advocates Hong Kong independence.

"The operation that we conducted yesterday was against a gangster inside a home-made laboratory inside a hostel in the Tsim Sha Tsui area.

"Those arrested wanted to produce TATP (triacetone triperoxide) and use it to attack some of the public facilities in Hong Kong, including the Cross-Harbour Tunnel, railways, courtrooms.

"They even wanted to lay bombs in rubbish bins on the street with a view to maximising the damage caused to society."

Mr Li noted that there was a good division of labour among those arrested.

"Some of them were responsible for providing the funds, providing money to the suspects. Some of them were responsible for purchasing the items they wanted, especially the chemicals.

"Some were what we call 'the scientists'. They were the ones who produced TATP inside the room. They had already conducted the recce - at at least two courtrooms in Hong Kong."

In the operation, Police seized some apparatus and equipment which are consistently used to produce TATP, a trace amount of explosives, some of the raw materials for making TATP, a number of telephones and communication devices that were believed to be used for launching the attacks.

They also seized some airguns and several operational manuals that outlined the details about the operation of the attacks - from producing TATP, how to lay the bombs, to departure plans.

Mr Li also appealed to the public to report any suspected terrorist activities to the department via various platforms.