HONG KONG (AFP) - Hong Kong police and protesters clashed early on Wednesday in some of the most violent scenes since pro-democracy demonstrations began more than a fortnight ago, leading to several arrests.

Hundreds of officers scuffled with protesters guarding newly erected barricades on a main road next to the city's government headquarters, using pepper spray to disperse those who defied orders to leave the area, according to an AFP journalist.

Within an hour police had regained control of the busy thoroughfare, which was occupied by protesters earlier in the day, dismantling hastily erected barricades and making dozens of arrests.

A wall of police marched on demonstrators clutching the umbrellas that have become emblematic of their fight for full democracy in the financial hub. They engaged in direct combat and knocked some protesters to the ground.

AFP saw several protesters being led away by police, with injuries on both sides.

The exact number of those arrested was not immediately available.

Journalists were jostled by police and warned they would not be treated differently if they breached a cordon.

Daniel Cheng, a reporter for an online news portal, told AFP: "(Police) grabbed me, more than 10 police, and they beat me, punches, kicks, elbows. I tried to tell them I'm a reporter but they didn't listen."

Cheng sported cuts to his lip and bruises on his neck and back. He said he was later released after showing his press card.

Earlier in the evening, protesters told AFP that they had decided to take over the highway, named Lung Wo road, after police cleared another occupied main road near the main Admiralty protest site without warning.

"We planned to take this road in retaliation," said Jeff Wong, 30.

"The government refuses to talk to us so we will keep occupying the roads until we get a real dialogue."

Protesters moved metal barricades inside a tunnel on Lung Wo road, blocking it to traffic.

The road, which runs east-west outside the government complex, had not been occupied before.

Huge crowds have intermittently rallied against China's insistence that it vet candidates standing for election as the semi-autonomous city's next leader in 2017 - a move protesters have labelled as "fake democracy".

While the activists have been praised for their civility and organisational skills, they have also brought widespread disruption.

Tempers are fraying, with shop owners and taxi drivers losing lucrative business and commuters voicing irritation at their disrupted journeys to work.

Angry and sometimes violent scuffles have frequently broken out between demonstrators and government loyalists, sparking accusations the authorities are using hired thugs.

Direct confrontation with police has been much less common, however. Wednesday's running battles were some of the most serious since Sept 28, when riot police fired tear gas at largely peaceful crowds.

In the last two days, officers have begun probing protester defences in raids aimed at opening some roads to traffic, while allowing the bulk of demonstrators to stay in place.

Police had vowed on Tuesday to tear down more street barricades manned by pro-democracy protesters, hours after hundreds of officers armed with chainsaws and boltcutters partially cleared two major roads occupied for a fortnight.

Barricades at two of the protest sites were dismantled early Tuesday with protesters putting up little resistance, sticking to their promise of non-violence.

Some protesters were seen sobbing as police went to work dismantling the protest sites on Tuesday.

"We are only residents and students!" one tearful young woman shouted at police. "We will leave as we are unable to fight you, but we will not give up."

Police said they would soon turn their attention to another secondary site in Mongkok, which has seen violent scuffles between protesters and opposition groups.

Protest leader Alex Chow reiterated a call for the city's chief executive Leung Chun-ying - whose resignation protesters are demanding - to restart stalled talks after the government abruptly cancelled dialogue last week.

"The Occupy movement will not retreat, there is no way to retreat right now... as long as Leung doesn't give a concrete solution, all the Occupiers will not leave," said Chow, president of the Hong Kong Federation of Students.

The renewed police offensive came a day after masked men rushed barricades in Admiralty, sparking accusations that thugs and suspected triads were being used to harass demonstrators and serve as a pretext for police to act.

On Monday embattled leader Leung said he hoped the protests would end "as quickly as possible".

A new poll released Tuesday by Hong Kong University showed Leung's support rating dropped 2.6 per cent from late last month to 40.6 per cent, his second-lowest rating since he came to office in 2012.