The clearance of Hong Kong's main pro-democracy camp is set to begin Thursday when bailiffs move in, authorities said, but some protesters vowed to stand their ground after more than two months of rallies.

A High Court ruling published Tuesday called for the clearance of three sections of the main Admiralty protest site, in the heart of Hong Kong's business district, where a tent city sprawls across a multi-lane highway.

Bailiffs will enforce the order on Thursday morning with authorities asking protesters to leave voluntarily before then.

But with reports saying that the clearance will go beyond the parameters of the injunction and take down the whole site, some at the camp have said they will resist.

"I think if they clear the whole of Admiralty, because the injunction is only for one area, people are going to react violently," one 27-year-old protester who gave his name as Alex told AFP.

"I don't agree we should leave without getting any progress."

Student-led demonstrators are demanding free leadership elections for the semi-autonomous Chinese city in 2017 -- but China's communist authorities insist that candidates must be vetted by a loyalist committee.

The injunction, requested by a local bus company, allows bailiffs to "request the assistance of police" where necessary in order to clear the site next to the government headquarters.

Bus company lawyer Paul Tse told reporters that the injunction would be enforced from 9:00 am Thursday (0100 GMT).

"We have the agreement that on Thursday morning at 9 o'clock we will apply the injunction. We are still arranging the details," Tse said, adding that he hoped protesters would "voluntarily retreat" before then.

Although the ruling only covers parts of the Admiralty protest zone, reports said that police -- who have always labelled the occupation illegal -- would clear the entire area, as well as a smaller protest site in the shopping district of Causeway Bay.

A third protest camp in the commercial zone of Mongkok was cleared late last month.

Protesters would stay "until the last minute" but not directly confront police, said a 31-year-old artist at the Admiralty site who gave his name only as Wong.

"You do see people moving from the court injunction area, but they are not retreating entirely," he said.

"I can't speak for everyone, but people here are willing to be arrested."

Police would likely clear Admiralty "including areas that are not covered in the injunction order" an unnamed police source told the South China Morning Post.

"We aim to clear all occupied roads and reopen traffic," the source said, adding that the action would take place Thursday.

The Causeway Bay camp could also be cleared that day, the source said.

Around 7,000 officers would be deployed, with announcements made beforehand to give protesters time to leave, The Standard newspaper said.

A police spokeswoman told AFP Tuesday that there was no further information on any clearance operation.

Authorities in Hong Kong and Beijing have said throughout that the mass street protests are "illegal" and have made no concessions to the students' demands for reform.