Hong Kong police said on Friday that rioters were deliberately creating "black terror" in the past week as they targeted shopping malls in various districts and "violently ruined" the Christmas period for people in the city.

Police told reporters at Friday's media briefing that rioters were using "mob-like" means, including trashing shops, throwing petrol bombs and hard objects from heights, to create havoc and threaten vendors to hand over their closed-circuit TV footage.  

"Rioters have deliberately created 'black terror' in the city, which has left residents living in fear and curbed freedom of speech," Chief Superintendent Kwok Ka-chuen said. "It's even difficult for residents just to go out on the street, eat out or go to the theater."

"We appeal to the public to not be afraid of rioters and their followers and bravely say no to violence," Kwok said, vowing strict enforcement of the law by police.

Black-clad rioters have vandalized several shops and businesses across various districts in Hong Kong, turning the Christmas festival into chaos.

The Hong Kong government said the acts were "outrageous."

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Hong Kong government calls Christmas Eve violence in city 'outrageous'

Speaking at Friday's briefing, police said 336 people – 244 males and 92 females – were arrested for offenses, including illegal gathering and possession of offensive weapons.

The people arrested are aged between 12 and 54, and 13 police officers were injured in the operation in the past week, Senior Superintendent Kong Wing-cheung of Police Public Relations Branch said.

Kong said 76 rounds of tear gas, 33 rubber bullets, 16 bean bags rounds and 12 sponge grenades were fired between Monday and Thursday.