Protesters are seen inside a chamber after they broke into the Legislative Council building in Hong Kong, Tyrone Siu / Reuters

Violence erupted in Hong Kong on Monday as hundreds of protesters stormed the legislature on the anniversary of the city's 1997 return to China.

Angry protesters destroyed pictures and daubing walls with graffiti in a direct challenge to China as anger over an extradition bill spiralled out of control.

Many of the demonstrators carried road signs, 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.

They even sat at legislators' desks, checking their phones.

Authorities while calling for an immediate end to the violence, has said that it had stopped all work on extradition bill amendments and that the legislation would automatically lapse in July next year.

A small group of mostly students wearing hard hats and masks had used a metal trolley, poles and scaffolding to charge again and again at the compound's reinforced glass doors, which eventually gave.

The council, the mini-parliament, issued a red alert, ordering the protesters to leave immediately.

It did not say what would happen if they didn't but police did not immediately intervene.

The Legislative Council Secretariat released a statement cancelling business for Tuesday. The central government offices said they would close on Tuesday "owing to security consideration."

Riot police in helmets and carrying batons earlier fired pepper spray as the standoff continued into the sweltering heat of the evening. Some demonstrators removed steel bars that were reinforcing parts of the council building.

Tens of thousands marched in temperatures of around 33 degrees Celsius (91.4°F) from Victoria Park in an annual rally. Many clapped as protesters held up a poster of Lam inside a bamboo cage. Organisers said 55,000 turned out.

More than a million people have taken to the streets at times over the past three weeks to vent their anger.

A tired-looking Lam appeared in public for the first time in nearly two weeks, before the storming of the legislature, flanked by her husband and former Hong Kong leader Tung Chee-hwa.

Agence France-Presse