Hong Kong is set to enact an emergency law to ban face masks at rallies, media reports, as authorities grapple with nearly four months of anti-government protests.

Many demonstrators wear face masks to hide their identities and shield themselves from tear gas.

The Hong Kong stock market jumped to a one-week high on the news, reported by media outlets TVB and Cable TV.

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The unrest, which began over opposition to a now-withdrawn extradition bill that would have allowed people to be sent to mainland China for trial, shows no sign of letting up.

Demonstrators, angry over the shooting of an 18-year-old this week by police, clashed with police into the early hours of Thursday.

AAP

Demonstrators threw petrol bombs and police responded with tear gas.

Police have also urged the government to impose curfews to help curb the escalating violence in the Chinese-ruled city, where officers have become a target of protesters amid accusations of excessive force.