Officers made a dawn raid at one rally site in the financial hub's bustling shopping district and hours later cleared away 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 the 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 tear gas 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 today, an AFP journalist at the scene reported, 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.

Within an hour, traffic was flowing freely along the newly cleared road although protesters still held onto a major carriageway opposite the city's legislative headquarters.

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."

At both sites 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.

They added they would increase patrols to ensure the newly cleared areas where not reoccupied.

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