Hong Kong’s embattled leader Carrie Lam invoked colonial-era emergency powers on Friday for the first time in more than 50 years in a dramatic move intended to quell escalating violence in the Chinese-ruled city.

Lam, speaking at a news conference, said a ban on face masks would take effect on Saturday under the emergency laws that allow authorities to “make any regulations whatsoever” in whatever they deem to be in the public interest.

But it was far from clear if the introduction of emergency powers would deter the protesters.Banks and shops in the busy Central district closed early in anticipation of violence as some protesters burned Chinese flags and chanted “You burn with us”.

“They can make use of the emergency law to enact any policies or laws that the government wants. There’s no rule of law anymore. We can only be united and protest.” Many protesters wear masks to hide their identity due to fears employers could face pressure to take action against them.

“We can’t keep the existing regulations idle and let violence escalate and the situation continue to deteriorate.” Lam described the territory as being in serious danger, but not in a state of emergency.

Pro-Beijing groups had been pushing for a mask ban but it was not clear how the government would implement it in a city where many of its 7.4 million residents wear them every day to protect against infection following the outbreak of the deadly Severe Acute Respiratory Syndrome in 2003.

Police can stop anyone in public and ask them to remove a mask if the officer believes it may prevent identification, according to the law. Exceptions are made if the person wearing a mask can prove they need it for medical, religious or professional reasons.

Offenders face a maximum fine of HK$25,000 and imprisonment for a year, according to details of the prohibition published by the government.

Four months of anti-government protests have plunged Hong Kong into its biggest political crisis since its handover from Britain to Beijing in 1997 under a “one country, two systems” formula granting it autonomy.