HONG KONG >> A mob of masked men opposed to Hong Kong’s pro-democracy demonstrators led an apparently coordinated assault on the protest zone in the heart of the city’s financial district Monday, tearing down barricades and clashing with police.

The chaotic scenes came after police carried out a dawn operation to reopen some key roads blocked by protesters for more than 15 days. Police said they will continue to chip away at the occupied zone to relieve traffic, and warned that anyone who challenges them could be arrested.

Monday’s confrontations highlighted the growing tension between student-led protesters and authorities — as well as other residents aggravated by the disruptions. The protesters, who had enjoyed widespread support when the movement began, are fighting to keep up momentum as the political crisis entered a third week.

Demonstrators have flooded several thoroughfares in central Hong Kong since Sept. 28 in a civil disobedience movement to oppose restrictions on the first-ever direct election for the semiautonomous Chinese city’s leader, promised by Beijing for 2017. They want authorities to drop a plan to use a pro-Beijing committee to screen candidates, and demand the resignation of Chief Executive Leung Chun-ying, the city’s deeply unpopular Beijing-backed leader.

Authorities have repeatedly urged protesters to retreat from the streets, but student leaders have vowed to keep up the disruptions until the government responds to their demands.

Protesters were rebuilding barriers Monday after about two dozen men wearing surgical masks to hide their faces tore at the metal barricades that demonstrators have put in place. The men, who used box cutters to snap the cable ties connecting the barricades, scuffled with protesters and police who tried to stop them.

An angry crowd of several hundred people then descended on the scene, rushing up to the barricades and attempting to storm the protest zone. They punched their fists in the air and chanted "Open the road!" About a dozen taxi drivers joined in, driving their cabs up to the barricades and leaning on their horns to express their anger over the traffic disruptions.

A line of police officers held the crowd back, keeping them separated from the protesters on the other side of the barriers.

It was not immediately clear who organized the anti-protest crowd, but some blamed triads, or organized crime gangs.

"Before the police came, young men wearing masks and dark clothing came to pick fights with people and we heard that some of them had weapons," said Kevin Ng, a college student who was at the scene and saw the scuffles. "I don’t know who the young men wearing masks were. We suspect they’re triad members, but it’s hard to say. What other kind of group would organize themselves to come attack us?"

One protester, Alex Kwok, said he received a scratch on his arm after he was attacked by several men whom he accused of being members of triads.

The tension later eased as most of the crowd dispersed. Police took away some masked men inside the protest zone who tried to pick fights with the protesters, and later said they arrested three men, aged 18 to 47, at the clashes on suspicion of assault and carrying weapons. Police did not say which side those arrested supported.

Allegations have surfaced that some people were paid to disrupt the protests. A local radio station broadcast an audio clip Monday in which a man, said to be a taxi driver, discussed a payment of 2,000 Hong Kong dollars ($258) to take part in the ruckus.

The clip could not be independently verified and it was not clear where the alleged payment was coming from.

Speaking to reporters at an event in Guangzhou, a city in southern China, Leung stressed that the authorities have handled the protests with a "huge degree of tolerance." He dodged a question about when officers will move in to clear the protests, saying only, "We cannot let this situation continue in the long term."

Leung also said, "I will not resign, and I don’t have to resign."

Earlier Monday, police removed some barricades on the edges of the protest zone to allow some traffic through the area.

Police stressed that the operation — carried out at dawn, when the number of protesters at the site is typically at its lowest — was not meant to clear the area, and said it was only to relieve traffic congestion for commuters heading to work.

Police spokesman Steve Hui said later Monday that officers would continue to trim the protest zone, but declined to elaborate.

Tens of thousands of protesters have occupied three busy business districts across Hong Kong to press their demands, but their numbers have since dwindled.

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Associated Press writer Joanna Chiu contributed to this report.