Hundreds of riot police in Hong Kong have lined up with shields and tear gas to clear campaigners who earlier broke into parliament.

Black-clad protesters wearing hard hats and face masks took over the legislative chamber after prying open metal gates to gain access as part of the latest wave of protests against contentious extradition legislation. 

Some carried road signs, others corrugated iron sheets and pieces of scaffolding upstairs and downstairs as about a thousand gathered around the Legislative Council building in the heart of the former British colony’s financial district.

Earlier police appeared to have retreated to avoid a confrontation, giving the protesters the run of the building.

Protestors used the time to smash and tear down portraits of legislative leaders and spray paint slogans on the wall and over the territory’s emblem.

Some stood on the desks of politicians while others climbed up to leave their messages on the soaring wooden wall.

One witness at the scene told Sky News that riot police are making “a very concerted effort at trying to move back the crowd right now”.

The witness said: “The police are holding up warning signs that read ‘disperse or we may use force.’”

Earlier, tens of thousands of others marched through the city to demand expanded democracy on the 22nd anniversary of the former British colony’s return to China.

The protesters say the Hong Kong government is not responding to their demands for a full withdrawal of contentious extradition legislation and the resignation of city leader Carrie Lam.

Frustration among protesters in Hong Kong earlier boiled over, with one group attacking the legislative building and tens of thousands of others marching through the city to demand expanded democracy on the 22nd anniversary of the former British colony’s return to China.

Earlier on Monday activists smashed a large hole through the bottom of a floor-to-ceiling window at the legislature. They repeatedly rammed a cargo cart and large poles into the glass while police with riot shields lined up inside to prevent anyone from entering.

However police officers were able to grab the cart after it became wedged in the broken glass and repel the protesters with pepper spray.

Five hours later, protesters smashed more windows and dismantled a towering metal grate protecting a section of the building, which was ordered to close and workers were sent home.

The government called for an immediate end to the violence, saying it had stopped all work on extradition bill amendments and that the legislation would automatically lapse in July next year.

There was no immediate response from the protesters.

The actions prompted march organisers 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 organisers said that would leave out many people who planned to join the march along the way.

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 Lam to resign.

Lam, who has come under fire 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 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 realise that I, as a politician, have to remind myself all the time of the need to grasp public sentiments accurately,” she told the gathering.

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.

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 organiser estimates.

Jimmy Sham, a leader of the pro-democracy group that organised the march, told the crowd 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.”

Britain remains “unwavering” in its support for Hong Kong and its freedoms, Foreign Secretary Jeremy Hunt has said.

After protesters in the former British colony took over the legislative chamber, Hunt said no violence was acceptable.

However, as tens of thousands took to the streets to demand greater democracy, Hunt tweeted that the right to peaceful protest must be preserved.

“Away from campaigning want to stress UK support for Hong Kong and its freedoms is UNWAVERING on this anniversary day,” he said.

“No violence is acceptable but HK people MUST preserve right to peaceful protest exercised within the law, as hundreds of thousands of brave people showed today.”

The foreign office has rejected Chinese accusations that Britain is “interfering” with the internal affairs of Hong Kong.

A Chinese foreign ministry spokesman said Britain should “know its place and stop interfering” in Hong Kong matters.

The foreign office, however, said the UK and China were co-signatories to the joint declaration on Hong Kong, originally agreed in 1984, which was a legally binding treaty deposited at the United Nations.

“By monitoring its implementation we are acting responsibly in line with our commitments, not interfering,” a spokeswoman said.

“Hong Kong’s rights and freedoms and high degree of autonomy underpin its success and prosperity.

“We will continue to stand up for these principles, including speaking out publicly and raising issues with the Chinese government when we have concerns.”