Hong Kong police vowed 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.

In a concerted effort to reduce the territory held by protesters, police tore down barricades in the bustling shopping district of Causeway Bay and on the edge of the main protest encampment in Admiralty, near the city government's headquarters.

They also vowed to target protester cordons in Mongkok, a working-class district known for its triad gangs where violence has previously broken out.

Huge crowds have intermittently rallied against China's insistence that it will 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 to an already densely populated city.

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

Police had been keeping a low profile at the three main protest sites after a decision to fire tear gas at peaceful demonstrators on September 28 caused outrage and encouraged tens of thousands to take to the streets.

But 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.

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

Hours later another contingent of officers tackled barricades at the main Admiralty site, using chainsaws to slice through bamboo poles and freeing up one of the multi-lane highways in the district.

At both sites protesters put up little resistance, sticking to their promise of non-violence.

Sobs and defiance

Some protesters were seen sobbing as police went to work dismantling the barricades.

"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 insisted they would soon turn their attention to Mongkok.

"Mongkok is already a high-risk area. Our officers are now ready to take action first to remove the obstacle there," Senior Superintendent Hui Chun-tak told reporters without giving a timeframe.

A similar clearance operation on Monday at the edges of the 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 cable ties and sticky tape to strengthen the structures -- even enlisting sympathetic construction workers for help.

But police Tuesday were well prepared for the myriad of obstacles, clearing them in less than an hour.

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 cancelled diaologue 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.

But some protesters admitted they would struggle to protect barricades from further attacks, particularly overnight when demonstrator numbers drop significantly.

"Of course it would be good if there were more disobedience acts (from protesters) but as you can see we don't have enough people," a 19-year-old chef who gave his surname Lau told AFP.

"I just do what I can," he said, adding this was his 14th day on the barricades.

The renewed police offensive comes 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 percent from late last month to 40.6 percent, his second lowest rating since he came to office in 2012.