Rioters set fire at Causeway Bay in Hong Kong, south China, Oct. 4, 2019 Photo: Xinhua

An improvised explosive device (IED) linked to a mobile phone exploded Sunday night in Kowloon, the first such case in Hong Kong, police said on Monday.

The bomb had only one purpose: to kill Hong Kong police officers, Explosive Ordnance Disposal Bureau officer Li Chin-chiu told a press conference on Monday. 

Li showed a picture of the explosion taken by a vehicle-mounted camera 8 pm about 10-15 meters from a group of police officers cleaning up barricades on Nathan Road. Nobody was injured in the explosion.

Officers found apparent bomb-making materials in the nearby shrubbery. It was a home-made bomb that could be controlled by a mobile phone, Li said, and the blast could have injured not only police but also civilians.

Hong Kong media reported the noise on Nathan Road in Mong Kok on Sunday night and said police found damaged wires, mobile phone batteries, circuit boards and telephone cards.

The explosive force of the bomb was fortunately not large enough to cause any casualties, Li said.

To create such a bomb required knowledge of chemistry and radio, he noted. The IED, the tactic as well as chemicals used  were similar to those used in terrorist attacks worldwide.   

Chris Tang Ping-keung, deputy commissioner of police (operations), stressed at the conference that it was the first time for such an attack and that the blast was "2 meters away to the police vehicle." 

Kong Wing-cheung, police public relations branch senior superintendent said 201 people aged between 14 and 62 were arrested from Friday to Sunday for alleged illegal assembly, possession of offensive weapons, arson and wearing masks at an illegal assembly. 

Twelve police officers were injured over the weekend, including one whose neck was stabbed and two who had their heads attacked, police said. 

The  Hong Kong Special Administrative Region government severely condemned the attacks and said police would bring those people to justice, according to a statement posted on its website on Monday.