Hong Kong Polytechnic University campus has become the latest battleground for long-running anti-government protests. Subscribe to our channel here: https://goo.gl/31Q53F
The violence is some of the worst seen during months of unrest in the semi-autonomous Chinese territory.
The protests started over a controversial extradition bill, and have now evolved into broader anti-government demonstrations.
China has warned that "no-one should underestimate [its] will to safeguard its sovereignty and Hong Kong's stability", and its ambassador to the UK said the central government would not sit back and watch if the situation became "uncontrollable".
Hong Kong is a part of China, and the protests are, in part, about the fear that the special freedoms the territory enjoys as a former British colony are being eroded.
International editor Gabriel Gatehouse and cameraman Jack Garland report. Report produced by Warwick Harrington.