Hong Kong leader Carrie Lam has banned protesters from wearing masks in a hardening of the government’s stance on the territory’s most disruptive crisis since it reverted to Chinese rule in 1997.

Ms Lam announced the ban at a news conference where she condemned a recent escalation of violence after four months of anti-government demonstrations.

The mask ban, imposed under a colonial-era emergency ordinance, takes effect on Saturday, and applies to unauthorised public gatherings and police-approved protests.

Carrie Lam
Carrie Lam (Vincent Thian/AP)

Ms Lam said she would go to the legislature later to get legal backing for the rule. She stressed that the use of emergency powers does not mean Hong Kong is in a state of emergency.

“People are asking can Hong Kong go back to normal? Is Hong Kong still a place where we can have our sweet home?” she said as she announced the ban.

“We must stop the violence. Now, it’s all over Hong Kong.”

Even as she wrapped up her announcement, protesters in masks and concealing themselves under umbrellas gathered in central Hong Kong.

Protesters in masks
Protesters vowed to defy the ban (Felipe Dana/AP)

Ms Lam said the ban targets violent protesters and rioters and “will be an effective deterrent to radical behaviour”. Masks will be permitted for “legitimate need”, when wearers can prove they need them for work, health or religious reasons.

The ban makes the wearing of full or partial face coverings, including face paint, at public gatherings punishable by a year in jail. A six-month jail term could be imposed on people who refuse a police officer’s order to remove a face covering for identification.

Ms Lam would not rule out a further toughening of measures if violence continues.

Hong Kong Protests
Thousands of masked protesters marched in the city’s business district (Vincent Yu/AP)

She said she would not resign because “stepping down is not something that will help the situation” when Hong Kong is facing “a very critical state of public danger”.

“We must save Hong Kong, the present Hong Kong and the future Hong Kong,” she said. “We can’t just leave the situation to get worse and worse.”

Thousands of masked protesters marched in the city’s business district before she spoke. They chanted “I want to wear face masks” and “Wearing a mask is not a crime”.

“Will they arrest 100,000 people on the street? The government is trying to intimidate us but at this moment, I don’t think the people will be scared,” one protester told an online live broadcast.

Hong Kong Protests
The protests have lasted months (Vincent Thian/AP)

At the nearby Causeway Bay shopping area, a huge crowd occupied streets to protest against the mask ban, and smaller rallies were held in several other areas.

Face masks have become a hallmark of protesters in Hong Kong, even at peaceful marches. As the use of police tear gas has become widespread, many young protesters have worn heavy duty gear including full gas masks and goggles.

Even peaceful masked marchers cite fears they could lose jobs and be denied access to schooling, public housing and other government-funded services if identified as having taken part in demonstrations.

Many also are concerned their identities could be shared with the massive state-security apparatus that helps keep the Communist Party in power across the border in mainland China, where hi-tech surveillance including facial recognition technology is ubiquitous.