As the 16th consecutive weekend of unrest continued, protesters were seen taking turns to run over a Chinese flag before defacing it, putting it in a bin, and pushing it into a nearby river.
At Sha Tin railway station, surveillance cameras were smashed, ticket sensors were knocked off gates and spray-painted, and the screens of ticket machines were smashed.
Many of the protesters used umbrellas to shield their identities.
A man suspected of advocating a pro-Beijing stance, who began attacking protesters, was beaten.
Police feared tear gas as they tried to advance on the protesters and disperse the crowds.
Inside a shopping centre in Sha Tin, objects were kicked over and fire extinguishers let off.
Police eventually moved in and many of the protesters were forced to run, with some of them being caught by heavily armed officers.
Sky’s Tom Cheshire, who was inside the Sha Tin mall, said: “It’s a pretty fast moving situation. They’ve been ripping bins off the wall, ready, because the police have been entering in full riot gear. It’s getting very chaotic.
“This started earlier in the day with people singing, doing sit-ins.
“The airport has very high security. There was no way the protesters were going to go there.
“It’s taken a really ugly turn. We were sitting when we saw a man with a bloody mess. He had been beaten up by the crowd. There was a mob around him baying for his blood. Eventually some of the protest medics came to his aid.”
A hardcore group of protesters say violence is necessary to attract the government’s attention. They are demanding the resignation of Hong Kong chief executive Carrie Lam, as well as an independent investigation into claims of police brutality.
Even though Ms Lam has agreed to withdraw a controversial extradition bill that triggered the protests back in June, the protesters are now calling for fully democratic elections in the semi-autonomous Chinese territory.
On Saturday night, police used tear gas and rubber rounds against protesters throwing gasoline bombs in their direction.
TV footage showed scenes of arguments and brawls, with people covered in blood.
At least three people were beaten with fists and umbrellas and kicked, and left bloodied and bruised.