The police used tear gas on Tuesday night to disperse a crowd that gathered near Tin Shui Estate in Tin Shui Wai to protest against the government's refusal to completely seal the border with the mainland despite growing fears about the Wuhan coronavirus.
Riot police raised warning flags before firing tear gas and rubber bullets near a shopping mall in Tin Shui Wai.
Officers also used pepper spray, with reporters also hit.
Police also stopped and searched people in Tseung Kwan O, Sai Kung and Mongkok, and made several arrests.
Police said in a statement that masked protesters "wreaked havoc at multiple locations, which included blocking Tong Tak Street in Tseung Kwan O, vandalising a shop in Shatin Plaza and throwing bricks outside Tin Shui Shopping Centre in Tin Shui Wai, posing a serious threat to public safety and public order".