Hundreds of police armed with chainsaws and boltcutters made a fresh assault on protest barricades in Hong Kong Tuesday, a day after a similar attempt backfired as demonstrators reinforced their defences.

Officers made a dawn raid at one rally site in the financial hub's bustling shopping district and hours later moved on a second set of barricades at the edge of the main protest encampment near the city's government headquarters.

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

While the activists have been praised for their civility and organisational skills they have also brought widespread disruption to an already densely populated and congested city usually renowned for its stability.

Angry and sometimes violent scuffles have broken out between demonstrators and government loyalists, sparking accusations that authorities are using hired thugs to sow trouble.

Police had been keeping a low profile at the three protests sites in Admiralty, Causeway Bay and Mongkok after a decision to fire teargas at peaceful demonstrators on September 28 caused outrage and encouraged tens of thousands to turn out on the streets.

But in the last two days, officers have begun probing protester defences in raids aimed at clearing some roads to ease traffic, while allowing the bulk of protesters to remain in place.

Around 150 police dismantled metal barricades at the Causeway Bay site before dawn Tuesday, an AFP journalist at the scene saw, freeing up traffic in one direction but leaving the protest camp there largely intact.

Hours later another contingent of officers hit barricades at the main Admiralty site, using chainsaws to slice through bamboo poles that had been used to reinforce protest cordons following a similar attempt to remove them on Monday.

- Sobs and defiance -

Some protesters were seen sobbing.

"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."

At both Causeway Bay and Admiralty, protesters put up little resistance.

Police told reporters that the operation was limited to removing barricades along key traffic routes and that the democracy campaigners would still be given space to express their views.

A similar operation on Monday at the edges of the sprawling Admiralty protest camp prompted activists there to swiftly regroup.

They laid down cement foundations and built up bamboo pole barricades blocking both lanes of a highway, using everything from steel chains to plastic ties and sticky tape to strengthen the structures, even enlisting sympathetic construction workers for help with their building work.

But police Tuesday appeared well prepared for the myriad of obstacles in their way.

Protest leader Alex Chow rallied supporters at Causeway Bay, and called on the city's chief executive Leung Chun-ying -- whose resignation protesters are demanding -- to restart stalled talks after the government abruptly pulled out 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 comes a day after masked men rushed the rebuilt 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.

Demonstrators, who have come under attack from organised crime gangs at another flashpoint demonstration site in Mongkok, shouted: "Weapons! Weapons!" and "Arrest the triads" as police struggled to impose order.

On Monday, embattled leader Leung told reporters in the Chinese city of Guangzhou that he wanted the protests to end.

"Under the appropriate situation we hope to allow society to return to normal as quickly as possible," he said on the sidelines of a trade meeting.