Fighting erupted in Hong Kong's parliament over planned changes to the law allowing suspects to be sent to mainland China for trial.
BBC reports several lawmakers were injured and one was taken to hospital as politicians clashed in the chamber.
Critics believe the proposed switch to the extradition law would erode Hong Kong's freedoms.
But authorities say they need to make the change so they can extradite a murder suspect to Taiwan.
One pro‑Beijing lawmaker called it "a sad day for Hong Kong".
Tensions boiled over with politicians swearing and jumping over tables amid a crowd of reporters as they fought to control the microphone.
Pro‑democracy legislator Gary Fan collapsed and was carried out on a stretcher, while one pro‑Beijing legislator was later seen with his arm in a sling.