Hong Kong police clashed with pro-democracy demonstrators Wednesday after a small group attempted to break into the city's legislature, with tensions spiking as court-ordered clearances of protest sites get under way.

Around 100 police used pepper spray and batons as they battled hundreds of protesters, some in helmets and waving umbrellas -- a symbol of their movement -- in an angry confrontation that broke out in the early hours. Officers made four arrests.

"Police strongly condemn such acts by the protesters, which disrupted public order," the police force said in a statement.

The clashes were sparked when a group of around a dozen protesters smashed their way through a side entrance to the southern Chinese city's Legislative Council using metal barricades as improvised battering rams.

"Smash it open then get inside," one protester was heard saying in footage aired by the local TVB channel.

A regular session of the chamber was cancelled on Wednesday and visitor tours of the complex were suspended, the government said in a statement.

Demonstrators have been camped on three major Hong Kong thoroughfares for seven weeks, demanding free leadership elections for the semi-autonomous city, but public support has ebbed as the weeks pass with little progress.

The authorities moved in for the first time to take down some barricades at the main protest camp Tuesday after a court granted an order to remove obstruction at the area, which is close to the legislative building.

"We want to escalate our protest," a masked protester told TVB. "The government has not responded to the demands of protesters and residents."

Police scouring the building on Wednesday took away at least one demonstrator who remained on the site as the working day began, according to the Apple Daily newspaper.

Beijing insists that candidates for the 2017 vote for the city's top post must be vetted by a loyalist committee -- an arrangement the protesters say will ensure the election of a pro-Beijing stooge.

The protests have largely been peaceful but have been punctuated with scuffles and clashes, and police used tear gas on large crowds at the main Admiralty protest site in late September.

Student protest leaders said after the latest confrontation that their movement is committed to non-violence.

"It's not something we like to see... We call on occupiers to stick firm to peaceful and non-violent principles and be a responsible participant of the umbrella movement," said 21-year-old Lester Shum from the Hong Kong Federation of Students.

A former British colony, Hong Kong was handed back to China in 1997 under a "one country, two systems" deal which guarantees civil liberties not seen on the mainland, including freedom of speech and the right to protest.

But concerns have been growing that these freedoms are being eroded, and frustrations have also been building over growing inequality in the freewheeling financial hub.