HONG KONG (AFP) - Hong Kong police swooped at dawn to clear the democracy protest site in Mong Kok on Friday morning, tearing down tents and barricades hours after the city's embattled leader reopened his offer of talks to end nearly three weeks of disruptive demonstrations.

The Mongkok site has seen violent scuffles between demonstrators calling for full democracy in the southern Chinese city and pro-government groups.

The dawn raid, which was met with no resistance from demonstrators, came as Chief Executive Leung Chun Ying renewed his offer for talks with student protesters a week after abruptly pulling out.

But the swift police operation risks throwing the talks into doubt as student leaders decide on their response to the raid, and defiant protesters who remained on one side of the multi-lane road that housed the camp debated over whether they should try to take it back overnight.

The Asian financial hub has been rocked by mass rallies for nearly three weeks calling both for full democracy and Leung's resignation. Ongoing sit-ins at three major intersections have caused significant disruption to a city usually known for its stability.

China has insisted that Leung's successor must be vetted by a loyalist committee before standing for election in 2017, a proposal protesters have dismissed as a "fake democracy".

The occupation of Mongkok - the second largest rally site and a densely packed working-class district known for its triad crime gangs - was a regular source of tension between protesters and many residents.

Demonstrators were attacked earlier in the month by masked thugs with suspected triad links, sparking angry scenes and accusations police did little to halt the assaults.

City authorities pulled out of talks with student protesters last week, plunging the two sides deeper into an impasse with no obvious ways out. Leung announced the reopening of talks with the Hong Kong Federation of Students (HKFS) Thursday while insisting police operations to clear protester barricades would continue.

HKFS official Ivan Law told AFP police action to clear Mongkok now threw doubt over those discussions, adding that the student union would meet to decide their response.

The raid began shortly before dawn as officers armed with boltcutters and saws descended on the camp, which straddled a major arterial road.

"It happened really fast," said 20-year-old protester Prince Yung Chung-To. "A lot of police came at 5 o'clock shouting they were going to clear the area."

Police were seen tearing down tents, barricades and umbrellas - the defining symbol of the democracy movement - and piling them into the back of a van. The clearance opened up traffic on one side of the road, but around 100 protesters remained on the opposite side in a significantly reduced area.

Some protesters advocated returning en masse to the site later in the evening in an attempt to wrestle it back.

"If we reach a consensus with the students we will encourage between 3,000 and 5,000 people to come down here tonight after work," Tam Tak-chi, an activist with pro-democracy group People Power, told AFP.

But police warned against any attempt to retake Mongkok.

"I emphasise that police will not tolerate further blockage of the reopened road by the radical protesters," police spokesman Hui Chun-tak told reports.

Some local residents cheered as the bulk of the protest camp was cleared and berated demonstrators who remained.

"How can I be not happy? Roads are for cars. We have to work," a woman in her 50s who only gave her surname Wong, told AFP.

"If students want to fight for what they want, just go to a park, make a noise," she added.

Confrontations have spiked in recent days as police began raiding protest sites and tearing down barricades near the government's besieged headquarters, with officers using pepper spray against crowds who angrily accused them of links to criminal triad gangs - a charge they deny.

Tensions soared further after video footage emerged showing plainclothes police officers beating a handcuffed demonstrator in the early hours of Wednesday during some of the most violent clashes since the protests began. The victim, a social worker and local party activists, was arrested after being seen throwing water over officers early Wednesday morning.

Seven officers involved in the beating video have been suspended pending an investigation.

The incident has become another public relations disaster for the police, who were severely criticised for firing tear gas on umbrella-wielding protesters on September 28 in a move that attracted worldwide attention.