Hong Kong police fired tear gas at protesters on Monday as a general strike plunged the Asian financial hub into fresh chaos.
Hundreds of flights were cancelled, while commuters struggled to get to work in the Monday morning rush hour, with many rail and bus services suspended.
As some train and bus services resumed, tens of thousands of demonstrators fanned out across several districts, where protests again degenerated into running clashes with riot police.
Speaking in a news conference on Monday morning, Hong Kong's embattled leader Carrie Lam said recent protests disrupting the former British colony are endangering the 'one country two systems' and destroying Hong Kong's prosperity.
"They say want a revolution and to liberate Hong Kong. These (actions) are already far beyond their original political demands, and challenges our national sovereignty and these illegal actions endanger the one country two systems and destroy Hong Kong's prosperity, " Lam said.
The Chinese-controlled city has been rocked by months of protests that began against a proposed bill to allow people to be extradited to stand trial in mainland China and have developed into calls for greater democracy.
Millions of people have taken to the streets to vent anger and frustration at the city's government, presenting the biggest popular challenge to Chinese leader Xi Jinping since he came to power in 2012.
China's official Xinhua news agency said on Sunday: "The central government will not sit idly by and let this situation continue. We firmly believe that Hong Kong will be able to overcome the difficulties and challenges ahead."