Hong Kong police have moved in on the main pro-democracy protest camp and started clearing tents.

A number of arrests have been made, with one protester reportedly shouting "We want democracy. We'll be back," as he was carried away.

Protesters were warned to disperse from the site or face arrest, in what is likely to be a final showdown after more than two months of demonstrations by the Occupy Central movement.

"Police will lock down the occupied area and set up a police cordon area ... If anyone refuses to leave police will take action to disperse or arrest," said senior officer Kwok Pak-chung.

Protesters were allowed to leave the site - made up of tents, art installations and supply stalls and stretching for a kilometre along the highway - during the 30-minute lockdown.

Bailiffs armed with cutters and pliers moved in first to remove barricades around the camp in the heart of the business district, but despite the police ultimatum a hardcore of a few hundred refused to leave.

There are fears that radical splinter groups will dig in for a last stand, after violent demonstrations outside a government building at the end of November.

The remaining crowds shouted their demands for free leadership elections, and vowed the clearance would not end the campaign, which has left relations with Beijing on a knife-edge.

Protesters were joined by more than 20 pro-democracy lawmakers and other prominent figures ahead of the police action.

Media mogul Jimmy Lai, a fierce critic of Beijing, said he would stay at the site "until I am arrested".

He said: "Definitely you will miss the people you have spent over two months with, other than that we're looking forward to the next one."

Pro-demovcracy lawmaker Claudia Mo said: "This is not the end of the movement. The political awakening amongst the young is irreversible and we will fight on."

The Admiralty site has been the focal point of protests since September, after China's Communist authorities insisted that candidates in Hong Kong's 2017 leadership election would have to be vetted by a loyalist committee.

Hong Kong's leadership had warned they would take "resolute action" against any protesters who resisted the clearance, which they said was being carried out to restore public order and reopen roads.