Dozens of police removed barricades from a second Hong Kong protest site on Tuesday, a day after a similar attempt at the city's main occupied area largely backfired as demonstrators rebuilt and reinforced their defences.

Around 150 police officers took away metal barricades in the bustling Causeway Bay shopping district shortly before dawn, according to an AFP journalist at the scene.

But the police only appeared to be targeting a single lane of traffic heading west into the city centre, telling demonstrators holding the tram lines and main routes heading east that they could stay put.

Demonstrators said the police operation began shortly after 5:00 am (2100 GMT).

"They just said the cars are going to come later and that they're not trying to remove us. They've said we can stay. We have to be calm, we've got about 15 people and there are more than 100 cops here," Billy Lee, a 36-year-old protester manning one of the barricades, told AFP.

Police had launched a similar operation on Monday, moving in to clear barriers at the edges of the main protest site in Admiralty, but protesters there swiftly regrouped.

Activists laid down cement foundations and built up bamboo pole barricades blocking both lanes of a highway, using everything from steel chains to plastic ties and sticky tape to strengthen the structures, even enlisting sympathetic construction workers for help with their building work.

Similar scenes had taken place Monday in Causeway Bay, which is one of the three main sites occupied by pro-democracy demonstrators who have paralysed parts of the city over the past fortnight.

Demonstrators erected a new barricade, filling buckets with concrete to place the feet of metal barriers inside and reinforcing their line with hundreds of plastic ties.

But the modifications did little to stop police from pulling the main barricades down Tuesday.

Causeway Bay is packed with luxury stores popular with tourists from mainland China and commands some of the highest retail rents in the world -- on a par with New York's Fifth Avenue.

Demonstrators had set up camp over a major east-west thoroughfare which usually carries buses, cars and trams, disrupting traffic and angering many locals who said business was being affected.

The atmosphere remained calm as police armed with bolt cutters and wire clippers sliced through plastic ties holding the barricades together, and ripped down banners with pro-democracy slogans on a bridge overlooking the site.

Although the police action cleared one side of the road protesters remained in control of the the eastbound carriageway running through the district as well as two tram lines.

Authorities accused of hiring thugs

On Monday masked men rushed the rebuilt barricades in Admiralty, sparking renewed accusations that authorities are using hired thugs to disperse demonstrators.

Demonstrators, who have come under attack from organised crime gangs known as triads at another flashpoint demonstration site in Mongkok, shouted: "Weapons! Weapons!" and "Arrest the triads" as police struggled to impose order.

Taxi drivers also converged on the site with their cars, demanding the barricades be removed and other anti-Occupy groups chanted "Occupy is illegal".

Students and pro-democracy campaigners have taken to the streets -- sometimes in their tens of thousands -- since last month to call for Beijing to change its position on allowing unfettered elections and to demand the resignation of the city's chief executive Leung Chun-ying.

Despite repeated orders to disperse, the sit-ins have taken on an air of permanence, with tents, portable showers and lecture venues springing up in recent days.

On Monday, embattled leader Leung had told reporters in the Chinese city of Guangzhou that he wanted the protests to end.

"Under the appropriate situation we hope to allow society to return to normal as quickly as possible," he said on the sidelines of a trade meeting.