Hong Kong bailiffs and police are planning to take action at pro-democracy protest sites in the city, as pressure grows on demonstrators to leave, the government said Tuesday.

Deputy leader Carrie Lam warned there was currently "no room for negotiations" between the authorities and protesters, urging them to move out of rally sites after a court authorised bailiffs to call on police if they were stopped from carrying out clearances.

"The police will stay in touch with the (court order) applicants and the bailiffs. We are making plans for actions that need to be taken. I believe that soon, police will get in touch with the relevant parties to make such preparations."

Lam did not say what shape the 'actions' would take, or give a timescale, and there was no immediate response from her office.

Police also declined to comment.

Now in their second month, demonstrators are occupying three sites around the city.

They are calling for fully free leadership elections in 2017, but Beijing has insisted that all candidates be screened by a loyalist committee which protesters brand "fake democracy".

"I strongly urge protesters who are still staying in the occupied areas -- whether the areas are covered by the injunctions or not -- they should voluntarily and peacefully leave... as soon as possible," Lam said.

Her comments came after the city's high court authorised police to back up bailiffs tasked with clearing parts of the Mong Kong and Admiralty sites, following court injunctions granted to transport groups and landlords.

Monday's order ruled that "any police officer be authorised to arrest and remove any person who the police officer reasonably believes or suspects to be obstructing or interfering (with) any bailiff in carrying out his or her duties".

Talks with the government over political reform have proved fruitless, with protest leaders now saying they want to take their demands direct to Beijing.

But China has consistently backed the Hong Kong administration, led by embattled chief executive Leung Chun-ying.

Lam said Tuesday that there was "no need" for student protest leaders to go to Beijing if they were only going to repeat previous demands.

She criticised them for not showing "sincerity" after their previous talks with the Hong Kong government.

"Instead their stance has become even more hardline," she said.

"I feel at this point... no room for negotiations exists."

Both Hong Kong and Beijing have branded the protests illegal.

Violence has flared sporadically during the weeks of demonstrations, with police using tear gas to disperse protesters on September 28, bringing tens of thousands onto the street in support.

Although numbers have dwindled, protesters are entrenched, having set up tents, food stalls and toilet facilities at the sites.

Protest leaders have said that the movement will continue to occupy key sites, despite the risk they may be forcibly removed.