Protesters clashed with riot police and plain clothes officers at Harbour City shopping mall in the Tsim Sha Tsui district of Hong Kong.
Some of the officers were seen hitting people with batons as others pushed bystanders back.
Riot police threatened some of the protesters with pepper spray during the melee which happened during busy Christmas eve trading.
It's been more than six months since the movement begain against a controversial extradition bill, then mushroomed into a sustained anti-government movement pushing for full democracy and other demands have burned through police manpower.
The movement has been successful in getting the government to shelve legislation that would have allowed Hong Kongers to be extradited to mainland China. But protesters have expanded their demands to include an investigation into police brutality, setting protesters free, and universal suffrage.
The latest clashes took place about a month after a local election resulted in a rise in pro-democracy candidates.