For the first time during the ongoing social unrest, a radio-controlled improvised explosive device went off in the busy district of Mong Kok on the night of October 13, in one of the most blatant attempts to seriously injure and even kill police officers on duty.

The home-made bomb had been planted in a flowerpot between Fife Street and Nathan Road, and was detonated as police officers parked their car and alighted to clear rioters' roadblocks just 10 to 15 metres from the bomb. At that time, apart from police officers, many reporters, protesters and bystanders were in the vicinity, who had not had a clue about the imminent danger that they were subjected to.

Senior Bomb Disposal Officer Alick McWhirter of the Explosive Ordnance Disposal Bureau spoke of the danger of the bomb explosion in an interview with journalists from Hong Kong and overseas. "Bombs are indiscriminate, and when functioned, will not distinguish between Police, members of the public or the press. Our preliminary examination at the scene, and of exhibits seized, suggests that this was a premeditated and calculated attack on Police in an attempt to kill or injure officers," he said.

Mr McWhirter said a thorough investigation was ongoing but he would not rule out that the explosive used was TATP, triacetone triperoxide, an extremely unstable and dangerous synthetic explosive. He added that alarmingly, the use of remote-controlled devices was often linked to terrorist attacks in both Southeast Asia and around the world.

In one intelligence-led operation, officers of the Narcotics Bureau (NB) raided a residential flat in Tai Kok Tsui on October 15 and seized raw materials for making explosives and petrol bombs, as well as a large amount of petrol, thinner, glass bottles and other essential ingredients for making petrol bombs. Notably, modified mobile phones that could have been used to trigger explosions were also found.

The successful raid led to the arrests of two males, aged 17 and 23, for unlawful assembly, possession of explosives and possession of offensive weapons.

Superintendent Raymond Chou of the NB led the operation and said had the explosives and offensive weapons been used, the consequences would be dire, "They would have caused heavy casualties and mass destruction of properties. The Police strongly condemn all forms of violence and warn of the danger of making and possessing explosives."