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People vandalize a Bank of China branch during a protest against a government ban on face masks.

Hong Kong erupted into further violence Friday — as protesters torched subway stations and vandalized Chinese banks in response to a ban on wearing masks.

The law passed by Chief Executive Carrie Lam was meant to deter anti-government protests, which have rocked the city for months, making it illegal for people to wear masks at public gatherings with the threat of up to one year in jail.

But the legislation, which comes into effect Saturday, only sparked more unrest. Demonstrators set fires outside subway entrances and sparked street battles across the island, The Wall Street Journal reported.

Clashes also broke out between protesters and police. One 14-year-old boy was shot in the leg by police according to local media reports, while officers in other parts of the city fired volleys of tear gas into crowds.

Demonstrators are unhappy with the city’s government and Beijing, which they say is interfering in Hong Kong’s autonomy.

Protesters used the masks to avoid being identified — fearing mainland China and local lawmakers were monitoring them through facial recognition technology, the Journal reported.

The riots have lasted four months and are the most disruptive crisis since the former British colony reverted to Chinese rule in 1997.