Officers used the gas to disperse demonstrators in Mong Kok and outside the Peninsula Hotel in Tsim Sha Tsui.

They also clashed with protesters inside shopping malls, where they used pepper spray and made multiple arrests.

Hundreds of demonstrators, many wearing masks, turned up at multiple locations and set a fire at a subway station entrance.

According to hospital authorities, 25 people were injured in the clashes, including one person who was in serious condition.

An HSBC building in Mong Kok was vandalised, with the message “Don’t forget Spark Alliance” spray-painted on walls, Radio Television Hong Kong reported. The slogan refers to a fund linked to pro-democracy protests.

“We are saddened and disappointed by the acts of vandalism and damage directed at our branch,” HSBC said in a statement posted on social media Wednesday morning.

Hong Kong’s pre-holiday strife extended more than six months of clashes between protesters and police, ignited by a proposed extradition law to allow fugitives to be sent to China to stand trial.

The unrest has also pushed the city into its first recession in a decade. Though the bill was withdrawn, protests have persisted with more demands, including direct elections of the city’s leader.

Protests will likely continue into the new year. Civil Human Rights Front, organiser of some of Hong Kong’s biggest peaceful protests, is calling for a march through the city centre on Jan 1. The organiser said it has applied for a police permit.