Hong Kong (CNN) Four people were injured during a knife attack outside a Hong Kong mall on Sunday, including a local politician whose ear was reported to have been partially bitten off.

The attack happened outside the Cityplaza mall in Tai Koo, where pro-democracy protests took place earlier in the day.

Three men and one woman are now being treated at the city's Pamela Youde Nethersole Eastern Hospital, a police source told CNN. Two of these are in a critical condition. The alleged attacked is also receiving treatment.

Among the injured was a pro-democracy politician whose ear was partially bitten off by the unidentified attacker, according to public broadcaster RTHK and the AFP news agency.

High-profile Hong Kong activist Joshua Wong tweeted that his "close colleague Dr Andrew Chiu was assaulted" and his "left ear was brutally halved."

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