Participants in two major protests, one on the island and another on the Kowloon peninsula, are expected to defy a ban on face masks that took effect at midnight on Friday, hours after embattled leader Carrie Lam invoked emergency powers.
Violent protests had erupted across the Asian financial centre soon after Lam wielded the colonial-era powers for the first time in more than 50 years to order the ban in hopes of curbing months of unrest.
The night's "extreme violence" justified the use of the emergency law, Beijing-backed Lam said on Saturday, when the city felt eerily quiet, with the subway and most shopping malls closed and many roads deserted.
Despite the closure of the metro, which carries about 5 million passengers a day, hundreds of anti-government protesters took to the streets, defying the ban on face masks, but had largely dispersed by evening.
Hong Kong's protests have plunged the city into its biggest political crisis in decades, posing the biggest popular challenge to Chinese President Xi Jinping since he came to power.
"These extreme radicals have rampant arrogance and behave vilely," China's representative Liaison Office in Hong Kong said on Sunday, denouncing Friday's destruction of one of its buildings by "extremist militants".
"We strongly condemn this and support the SAR government and the police to severely punish illegal violent elements in accordance with the law," it said in a statement, referring to Hong Kong's status as a special autonomous region of China.
Rail operator MTR Corp said it would not open some stations on Sunday, as it needed time to repair vandalised facilities, and also cut short operations by more than three hours, to end at 9 p.m.
Most supermarkets and commercial stores reopened after the previous day's closures, although some malls, such as Sogo in the bustling Causeway Bay commercial district and IFC in Central, remained shuttered.
Global luxury brands from Prada to Cartier are counting the costs as the unrest has kept tourists away, taking retail sales down 23% in August, their biggest decline on record.
Many restaurants and small businesses have had to shut repeatedly, with the protests pushing Hong Kong's economy to the brink of its first recession in a decade.
The increasingly violent protests that have roiled the former British colony for four months began in opposition to a bill that would have allowed extradition to mainland China, but have spiralled into a broader pro-democracy movement.
Lam said the ban on face masks, which many protesters use to conceal their identities, was ordered under the emergency laws that allow authorities to "make any regulations whatsoever" in whatever they deem to be in the public interest.
But it enraged protesters, who took to the streets on Friday to vent their anger, many of them masked in open defiance. Some set fires, hurled petrol bombs at police and burned the Chinese national flag, in a direct challenge to authorities in Beijing.
The current "precarious situation", which endangered public safety, left no timely solution but the anti-mask law, Matthew Cheung, Hong Kong's chief secretary, wrote on his blog on Sunday.
He urged people to oppose violence ahead of grassroots district council elections set for Nov. 24.
Financial Secretary Paul Chan also addressed the protests in his blog, saying that despite recent obstacles, Hong Kong's banking system remained sound and the financial market was functioning well.
Protesters have taken aim at some of China's largest banks, trashing ATM machines at branches of Bank of China's Hong Kong unit, for example, while nearby international counterparts, such as Standard Chartered, have escaped untouched.
Chan's comment came after Hong Kong's Monetary Authority said about 5% of the city's ATMs could not transact cash withdrawals for 'various reasons.'
The Hong Kong Association of Banks (HKAB) condemned violent acts "which have caused serious damage to some bank branches and ATMs".
Protesters are angry at what they see as creeping interference in Hong Kong, which Britain returned to China in 1997 under a "one country, two systems" formula guaranteeing freedoms that are not enjoyed on the mainland.
China dismisses the accusation, saying foreign governments, including Britain and the United States, have fanned anti-China sentiment.