The Hospital Authority said 31 people had been sent to hospital, including two in critical condition.

Ninety-six protesters will be charged with rioting offences and face the West Kowloon Magistrates’ Court on Wednesday, according to The South China Morning Post. It marks the largest round of prosecutions since demonstrations began in June over a now-shelved extradition bill that activists say was an example of how Hong Kong citizens' freedoms and rights are being eroded.

The newspaper also reported a police source had confirmed live "warning shots" had been fired at Tsuen Wan, where the student was shot, and Yau Ma Tei.

A video of the incident at Yau Ma Tei showed a violent confrontation between police and protesters.

Demonstrators were seen swarming a police van and attacking officers with poles and makeshift weapons, while people in police uniforms were seen striking protesters with batons.

Earlier, Hong Kong police issued a statement on social media confirming reports that a reporter and camera operator were injured in an acid attack.

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“Rioters have used corrosive liquid in the Tuen Mun area, injuring multiple officers and reporters. Police strongly condemn the violent acts and appeal to members of the public to mind their personal safety,” the statement said.

A fire broke out outside the Hopewell Centre in Wan Chai, as well as at the Wong Tai Sin offices of Beijing-aligned legislators Wong Kwol-kin and Ho Kai-ming. Hong Kong police issued warnings telling people to stay indoors.

The smell of stinging tear gas and smoke from street fires started by protesters engulfed the Wan Chai, Wong Tai Sin, Sha Tin, Tuen Mun, Tsuen Wan and Tsim Sha Tsui areas. Using umbrellas as shields, protesters hurled gasoline bombs, bricks and other objects at police, who responded with volleys of tear gas.

In Wong Tai Sin, a gasoline bomb that protesters hurled at police exploded near motorcycles parked along a pavement, creating a large blaze that was put out by firefighters. Some protesters placed an emergency water hose down a subway station to try to flood it.

A water cannon truck sprayed blue water, used to identify protesters, to disperse crowds from advancing to government offices in the city. Scores of police officers also stood guard near Beijing's liaison office as the battle continued.