Tension spiked at democracy protests that have gripped Hong Kong for nearly two months as police arrested four men early Wednesday after a small group of activists tried to force their way into the city's legislature in overnight clashes.

The arrests came after authorities cleared some barricades a day earlier from a small section of a site occupied by pro-democracy activists for more than 50 days.

Police used pepper spray, batons and riot shields against the umbrella-wielding protesters wearing masks, goggles and hardhats, who they said repeatedly charged their cordon and injured three officers.

The protesters used metal barricades and concrete slabs to smash glass doors at the legislature before officers police rushed in to push them back.

Pro-democracy lawmaker Fernando Cheung tried to intervene but was pulled aside by some protesters so that others could continue ramming the glass.

Cheung told reporters that he saw one person enter the building.

The violence apparently involved protesters who organized their action through an Internet forum with a reputation for attracting people with radical views.

Cheung and other lawmakers from the so-called "pan-democrat" camp condemned the violence, saying it undermined the non-violent civil disobedience movement.

The clashes and the court-ordered barricade clearance hours earlier underscore the protest movement's turn to a riskier phase as student leaders run out of options.

The student-led democracy protesters reject restrictions laid down by Beijing on inaugural 2017 elections for the southern Chinese financial hub's top leader. But the students have been fighting to maintain momentum as the protest drags on, with the Hong Kong government appearing to adopt a strategy of standing by in hopes it fizzles out.

The students' requests to talk to China's communist leaders in Beijing have been rebuffed and three student leaders were prevented from flying to Beijing on the weekend to try to contact the officials directly.