Hong Kong's leader has invoked rarely-used emergency powers to ban people from wearing face masks during public assemblies, a move likely to infuriate the thousands of mainly young people involved in the months-long protest movement.

The ban will come into effect on October 5, Chief Executive Carrie Lam announced at a press conference on Friday following a special meeting of her cabinet, the Executive Council.

In anticipation of the announcement, hundreds of people marched through Hong Kong’s central business district in protest against the ban. More protests are planned for the evening.

Lam said the order to enact the “Prohibition On Face Covering Regulation” was a “necessary decision” but insisted it does not mean Hong Kong was in a state of emergency.

“We are now in a rather extensive and serious public danger. It is essential for us to stop violence and restore calm to society as soon as possible,” she said.

Lam said she won’t set a date to nullify the anti-mask law.

The vast majority of people who have attended the city’s recent pro-democracy demonstrations do so wearing masks to hide their identity, fearful that they could be arrested or targeted by police. Gas masks and respirators to protect against tear gas, which is often used by authorities to disperse unauthorized gatherings, have also become commonplace.

In order to enact such a ban the Chief Executive Office will invoke the city’s colonial-era Emergency Regulations Ordinance, which grants the government sweeping emergency powers.

The new law bans people from wearing facial coverings that obscure their identity, including paint, at unauthorized or authorized protests, or public processions. Those found guilty face up to a year in prison and a HKD $25,000 ($3,100) fine.

Lam said the regulation contains exemptions for people who do have legitimate reasons to wear face coverings – such as for religious, medical, or professional purposes.

Mounting pressure

Lam is facing mounting pressure to end the ongoing protests, which are set to enter their 18th weekend. Protests in the semi-autonomous city have grown increasingly violent since they began in early June.

Hong Kong’s Secretary of Justice John Lee said at the press conference Friday that protesters acted more aggressively when they wore masks and it allowed those committing criminal acts to escape legal action.

But critics say the law would set a dangerous precedent and pave the way for harsher regulations.

The Civil Human Rights Front, whose marches have attracted hundreds of thousands of people, said the anti-mask law would “further suppress citizens and aggravate the contradiction between society and the political power, further pushing Hong Kong into the abyss.”

Speaking to CNN last week, a senior adviser to Hong Kong leader Carrie Lam – who spoke on background to be candid about government thinking – said they were concerned that any declaration of an emergency by the Hong Kong government could enable Beijing to intervene. The laws which cover the central government doing so are all structured around an emergency situation.

“If we ourselves declare there is a state of emergency we’re halfway there,” the adviser told CNN.

The announcement comes after an officer fired a live round into a protester for the first time on Tuesday, when thousands took to the streets as Beijing celebrated the 70th anniversary of the founding of the People’s Republic of China.

The teenage protester who was shot is under arrest for assaulting a police officer and could face further arrests for rioting, a source told CNN. He is in stable condition, the Queen Elizabeth Hospital’s media department said on Wednesday.

The political crisis began after hundreds of thousands took to the streets to oppose a controversial bill that would have legalized extradition from Hong Kong to mainland China. The city’s leader, Carrie Lam, has promised to withdraw the bill once the city’s legislature resumes. But the movement has snowballed into a grass-roots, decentralized crusade for universal suffrage and independent inquiries into alleged police misconduct.

In total since the anti-government protests began in June, 1,100 people have been injured, including 300 police officers, Lam said.