Hong Kong's leader Carrie Lam has condemned what she called the "extreme use of violence" by protesters who stormed and vandalized the territory's parliament on Monday night.
Activists occupied the Legislative Council (LegCo) for hours after breaking away from a peaceful protest.
The unrest follows peaceful protests sparked by a divisive extradition bill.
The chief executive held a pre-dawn press conference after police had fired tear gas to clear LegCo.
Flanked by Police Commissioner Lo Wai-chung, she said the actions of those who broke into LegCo were "something that we should seriously condemn, because nothing is more important than the rule of law in Hong Kong".
The government suspended the extradition bill last month and it is now unlikely to pass, but the protesters want it scrapped completely and are calling on Ms Lam to stand down.
What happened on Monday?
Monday was the anniversary of Hong Kong's handover from British to Chinese rule in 1997.
The day is usually marked by an annual pro-democracy march, but this year's event followed weeks of unrest in the city over a controversial extradition law.
Critics have said the law could be used to send political dissidents from semi-autonomous Hong Kong to mainland China.
There were some scuffles in the early morning, as protesters blocked streets around the venue where Ms Lam was attending the annual flag-raising ceremony.
At around midday, dozens of demonstrators broke off from the main protest and made their way to LegCo.
They effectively besieged the building, as a large crowd of several hundred watched from a distance, before eventually smashing their way through the glass facade.
Inside, they defaced the emblem of Hong Kong in the central chamber, raised the old British colonial flag, spray-painted messages across the walls and shattered furniture.
At about midnight outside the building, protesters clad in plastic helmets and brandishing umbrellas retreated from a baton charge by riot police, who quickly overcame their makeshift barriers.
Within an hour, the streets around the building were clear of everyone except the media and police
What did Carrie Lam say?
Speaking in the early hours outside the police headquarters, Ms Lam said it was a scene that "really saddens… and shocks a lot of people".
She contrasted Monday's tumultuous events with the annual peaceful march on 1 July, which she said reflected "the core values we attach to peace and order" in Hong Kong.
Ms Lam showed little emotion as she stressed the importance of maintaining the rule of law in Hong Kong.
"I hope the community at large will agree with us that with these violent acts that we have seen, it is right for us to condemn it, and hope society will return to normal as soon as possible," she told reporters.
She strongly denied she could be blamed for failing to address the protesters' demands, saying the government had "not responded to every demand asked because of good reasons".
The extradition bill would now expire with the end of the government's term, she said. "That is a very positive response to the demands that we have heard."
She also argued that granting an amnesty to all protesters would not be "in accordance with the rule of law".
In an apparent warning to protesters, Ms Lam said Hong Kong's authorities would "pursue any illegal acts" carried out by demonstrators.
Why are people protesting?
Hong Kong is part of China but run under a "one country, two systems" arrangement, that guarantees it a level of autonomy, and rights not seen on the mainland.
Protests began in June, focusing on the extradition laws. But they have broadened to include the release of all detained activists and investigations into alleged police violence, as well as general concerns over Beijing's influence eroding the territory's rule of law and special rights.
Last month's demonstrations forced the government to apologise and suspend the planned extradition law.
However, many protesters have said they will not back down until the bill is completely scrapped. Others are also calling for Ms Lam to step down.
What has China said?
There has been no official Chinese reaction to the latest protests.
The state run Global Times newspaper on Tuesday condemned what happened as "nothing short of mob-like behaviour".
"Out of blind arrogance and rage, protestors showed a complete disregard for law and order," an editorial in the English-language paper said.
Before the violence at night, US President Donald Trump on Monday had expressed his support for the protesters.
He said the demonstrators were "looking for democracy," adding that "unfortunately, some governments don't want democracy".
The UK Foreign Minister Jeremy Hunt said at the weekend there was "unwavering" support for "Hong Kong and its freedoms" but urged restraint from protesters.
He said the rights of Hong Kong, as agreed in the handover, were "a legally-binding treaty and remains as valid today as it did when it was signed and ratified".
Taiwan's Foreign Minister Joseph Wu said the people of Hong Kong were "seething with anger and frustration."
In a tweet late on Monday evening, he said the idea of "one country, two systems" was "nothing but a lie" and urged the global community to "support the people's struggle for freedom and fully democratic elections".