Violence has erupted once more across Hong Kong as defiant masked protesters rampaged and police fired tear gas, hours after the city's embattled leader invoked rarely used emergency powers to ban masks at rallies.
Challenging the ban, set to take effect on Saturday, thousands of protesters crammed streets in the central business district and other areas, shouting "Hong Kong people, resist".
Pockets of angry protesters later attacked Chinese bank outlets, vandalised subway stations and set street fires, prompting police to respond with tear gas in many areas.
City chief executive Carrie Lam said at a news conference that the mask ban, imposed under a colonial-era emergency ordinance that was last used over half a decade ago, targets violent protesters and rioters and "will be an effective deterrent to radical behaviour".
The ban applies to all public gatherings, both unauthorised and those approved by police. Masks will be permitted for "legitimate need" when wearers can prove they need them for work, health or religious reasons.
Ms Lam stressed it does not mean the semi-autonomous Chinese territory is in a state of emergency. She said she would go to the legislature later to get legal backing for the rule.
"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.
Even as she wrapped up her announcement, protesters in masks and concealing themselves under umbrellas were gathering.
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.
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.
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.