Rioters set fire on road outside of the Hong Kong Polytechnic University in Hong Kong, South China, November 17, 2019. Photo: Xinhua

The Hong Kong police on Monday clarified rumors that it raided the  Hong Kong Polytechnic University (PolyU) on Sunday night and Monday morning, saying it only conducted arrests and dispersion operations after the rioters lingered on the campus despite police's warning and kept challenging police.

At 5:30 am on Monday, the police entered the campus and detained a few masked rioters while radical mobs that stayed at the campus in Hung Hom set a massive fire at the school entrance and ignored repeated police warnings to leave.

"In the past week, the rioters could enter the PolyU freely and we have left sufficient time for them. But despite constant warnings from us demanding them to leave, some still stayed in the university until Sunday night," noted the police at a routine press conference on Monday.

Among the arrested included so-called volunteers, medical staff and journalists, who could not show valid professional credentials when asked, according to the police. 

"We targeted all those remaining in the university, as our intelligence showed that some rioters may just change clothes to escape arrests," said a police spokesman.

Over the past week, the police arrested 154 people suspected of unlawful assembly, rioting and possession of deadly weapons, according to the police.

Standoffs between rioters and the police near the campus of PolyU started Saturday night. Rioters set fire to several pedestrian bridges and a police armored car, and threw Molotov cocktails at the police, prompting the police to fire tear gas and use water cannons to disperse them. 

On Sunday afternoon, a police officer from the Force Media Liaison Cadre was shot with an arrow. Another officer was hit by a marble on his mask but did not sustain injuries. On Sunday night, a rioter drove a car at police and crushed one from behind. One officer fired a live round at the vehicle. 

Local media reported that hazardous chemicals had been stolen from multiple campus laboratories of PolyU on Saturday night. The university reported the stolen chemicals to police as university officials believe they posed a severe threat to public safety.

"As these chemicals are either combustible, corrosive or toxic and can cause detrimental harm, we urge rioters to take into consideration of citizens and not use any chemicals," said the police, who said the university has become an arsenal. 

Li Kwai-wah, senior superintendent of Organized Crime and Triad Bureau, said the police deem the terror threat level in Hong Kong as "moderate."

Regarding a ruling by Hong Kong's High Court on Monday saying the anti-mask law adopted by the HKSAR government to quell months-long protests was "unconstitutional," Li noted that the law was helpful in deterring protesters, but will suspend enforcing the law in accordance with the ruling.

54-year-old Chris Tang Ping-keung, known for his hardline approach, will replace Stephen Lo Wai-chung as the commissioner of police of the Hong Kong Police Force. Expectations are running high as to whether he would end the months-long protests that have deteriorated Hong Kong's security.