HONG KONG (AP) — Hundreds of protesters in Hong Kong swarmed into the legislature’s main building Monday night, tearing down portraits of legislative leaders and spray-painting pro-democracy slogans on the walls of the main chamber as frustration over a lack of response from the administration to opposition demands boiled over.

Police carrying riot shields and firing tear gas moved in shortly after midnight to clear surrounding streets and then moved into the already vacated legislative chambers. A spokesman had earlier broadcast a warning that “appropriate force” would be used in the clearance operation, but there was no immediate word on any arrests or injuries.

The flashing blue and red lights of dozens of police vans and buses lit up the abandoned streets leading to the legislature.

The sharp escalation in tactics came on the anniversary of the former British colony’s return to China, a city holiday, and reflected mounting frustration with Hong Kong’s leader for not responding to protesters’ demands after several weeks of demonstrations.

The protesters whacked away at thick glass windows until they shattered them and then pried open steel security gates which they propped open to gain entrance to the building. Police in riot gear retreated as the protesters entered about 9 p.m., avoiding a confrontation and giving them the run of the building.

They stood on lawmakers’ desks in the main legislative chamber, painted over the territory’s emblem high up on a wooden wall and wrote slogans calling for a democratic election of the city’s leader and denouncing now-suspended extradition legislation that sparked the protests. Many wore yellow and white helmets, face masks and the black T-shirts that have become their uniform.

Police announced about 10:30 p.m. that they would clear the area, asking protesters to leave.

The actions prompted organizers of a separate peaceful march against the extradition bill to change the endpoint of their protest from the legislature to a nearby park, after police asked them to either call it off or change the route. Police wanted the march to end earlier in the Wan Chai district, but organizers said that would leave out many people who planned to join the march along the way.

Police estimated 190,000 people joined the peaceful march, the third major one in as many weeks. Organizers estimated the number at 550,000.

Hong Kong has been wracked by weeks of protests over a government attempt to change extradition laws to allow suspects to be sent to China to face trial. The proposed legislation, on which debate has been suspended indefinitely, increased fears of eroding freedoms in the territory, which Britain returned to China on July 1, 1997.

Protesters want the bills formally withdrawn and Hong Kong’s embattled leader, Carrie Lam, to resign.

Lam, who has come under withering criticism for trying to push the legislation through, pledged to be more responsive to public sentiment but has not responded directly to protesters’ demands.

In an address after a flag-raising ceremony marking the anniversary of the handover, Lam said the protests and two earlier marches that attracted hundreds of thousands of participants have taught her that she needs to listen better to youth and people in general.

“This has made me fully realize that I, as a politician, have to remind myself all the time of the need to grasp public sentiments accurately,” she told the gathering in the city’s cavernous convention center.

She insisted her government has good intentions, but said “I will learn the lesson and ensure that the government’s future work will be closer and more responsive to the aspirations, sentiments and opinions of the community.”

Security guards pushed pro-democracy lawmaker Helena Wong out of the room as she shouted at Lam to resign and withdraw the “evil” legislation. She later told reporters she was voicing the grievances and opinions of the protesters, who could not get into the event.

Mainland China’s entirely state-controlled media made no mention of Monday’s protests. The main evening news broadcast carried video of the flag-raising ceremony, along with parts of Lam’s address and shots of Hong Kong residents praising displays put on by the People’s Liberation Army garrison in the territory.

Chinese media outlets have barely reported on the protests since they began last month, other than to blame foreign forces for stirring up unrest.

The extradition bill controversy has given fresh momentum to Hong Kong’s pro-democracy opposition movement, awakening broader concerns that China is chipping away at the rights guaranteed to Hong Kong for 50 years under a “one country, two systems” framework. The two marches in June drew more than a million people, according to organizer estimates.

Jimmy Sham, a leader of the pro-democracy group that organized Monday’s march, told the crowd that Lam had not responded to their demands because she is not democratically elected. The leader of Hong Kong is chosen by a committee dominated by pro-China elites.

“We know that Carrie Lam can be so arrogant,” Sham said, rallying the crowd under a blazing sun before the start of the march at Victoria Park. “She is protected by our flawed system.”

The protesters are also demanding an independent inquiry into police actions during a June 12 protest, when officers used tear gas and rubber bullets to disperse a demonstration that blocked the legislature on the day that debate on the bill had been scheduled to resume.

The police say the use of force was justified, but since then have largely adopted softer tactics, even as protesters besieged police headquarters in recent days, pelting it with eggs and spray-painting slogans on its outer walls.

The area around Golden Bauhinia Square, where the flag-raising ceremony took place, was blocked off from Saturday to prevent protesters from gathering to disrupt it. Before the morning ceremony, protesters trying to force their way to the square were driven back by officers with plastic shields and batons, the retreating protesters pointing open umbrellas to ward off pepper spray.

“We are horrified, this is our obligation to do this, we are protecting our home,” said Jack, a 26-year-old office worker who would only give his first name. “I don’t know why the government is harming us. It’s harming the rule of law, the rule of law is the last firewall between us and the Chinese Communist Party.”

The extradition legislation has drawn opposition from the legal profession, commercial groups and foreign nations, reflecting Hong Kong’s status as an international business center with a strong independent judiciary and high degree of transparency.

During a brief visit to Mongolia on Monday, U.S. National Security Adviser John Bolton said Washington expects “China like every other country to adhere to its international obligations” regarding Hong Kong.

China rejects all such statements as foreign interference. In Beijing, Chinese foreign ministry spokesman Geng Shuang told reporters at a daily briefing that “Hong Kong affairs are purely China’s internal affairs, and no foreign country has the right to intervene.”

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Associated Press journalists Raf Wober, Alice Fung, Johnson Lai and Dake Kang in Hong Kong and Christopher Bodeen in Beijing contributed to this report.