Hong Kong authorities are vehemently denying they used organized crime gangs against pro-democracy protesters in attempts to stir more violence and clear the streets overnight.
Security chief Lai Tung-kwok said Saturday such rumors are completely unfounded and utterly unfair.
Hong Kong police have arrested 19 people during a night of violence between pro-democracy protesters and mobs trying to drive the protesters from the streets.
Police said Saturday some of those arrested are believed to have connections to organized crime gangs, known as triads.
Local media say at least 18 people, including several police officers, were injured in the clashes.
On Friday, pro-democracy student protesters called off talks with Hong Kong's government after violent clashes broke out with opponents of the demonstrations.
The Hong Kong Federation of Students said authorities failed to intervene in "organized attacks" on demonstrators in several main protest sites, including the Mong Kok neighborhood.
Fights broke out when hundreds of supporters of Communist Party rule attacked a protest site in Mong Kok, smashing tents and tearing down banners.
Tens of thousands of protesters have occupied some of Hong Kong's busiest streets for more than a week, stifling traffic and business activity. The protesters are demanding that China allow democratic elections in 2017 and for Hong Kong's Beijing-friendly Chief Executive Leung Chun-ying to resign.
On Thursday, Leung said he is sending his chief secretary to meet with student protesters, who form a large segment of the demonstrators, in an attempt to resolve the political crisis.
The protests mark the biggest unrest in Hong Kong since Beijing took control of the one-time British colony in 1997.
The scuffles in Kowloon's crowded Mong Kok district and other areas were the most chaotic since police used tear gas and pepper spray last Sunday to try to disperse the protesters.
Hong Kong police were forced to intervene Friday after street fights broke out between pro-democracy protesters and groups of people who said they were frustrated residents who opposed the week-long protests.
Police formed a human chain in an attempt to separate the two groups. When the barrier did not hold, more police were sent in as reinforcements.
VOA correspondent Brian Padden, who is in Mong Kok, described the situation as "very volatile."
"These angry individuals - no one is sure who they are or where they come from. They say they are businessmen and workers from the area," Padden said.
"We don't know if there is any sort of organization to why they are here, or if they just heard something on TV and all came running and have just had enough and have been waiting for this opportunity to express how angry they are about this democracy movement," he added.
The pro-democracy protesters - mainly students - accused the Beijing supporters of coming to the area to cause trouble.
It was unclear if the mob of people in their 30s and older trying to drive away the mostly younger protesters were an organized group. But at least some were local residents fed up with the inconvenience of blocked streets and closed shops. Stern orders by the police to stop blocking the way may have encouraged them to act on their own.
Benny Tai, leader of the broader pro-democracy movement Occupy Central With Love and Peace urged protesters to shift back to the Admiralty area, near the government headquarters, where they began their protests last weekend, for safety's sake.
Tens of thousands of protesters have taken to Hong Kong's streets in the past week to demand full democracy in the former British colony, including a free voting system when they come to choose a new leader in 2017.
The unrest followed heavy rainstorms on Friday that had reduced the number of pro-democracy protesters to just several dozen. Many protesters had also returned to work following a two-day holiday.
Many activists worry authorities will take advantage of the dwindling numbers to clear the protest sites, which have been occupied with tens of thousands of people since last Friday.
Hong Kong leader Leung Chun-ying offered a concession by agreeing to open talks with pro-democracy protesters but refused to stand down. But Beijing restated its resolute opposition to the protests and a completely free vote in Hong Kong.
Beijing, facing separatist unrest in far-flung and resource-rich Tibet and Xinjiang, is unlikely to give way in Hong Kong, fearful that calls for democracy there, especially if successful, will spread to the mainland.
And Financial Secretary John Tsang warned that sustained protests in the city's Central financial center could create “permanent” damage to the Asian financial hub.
China's Communist Party has declared the protests to be illegal and in a state media editorial on Friday warned the campaign of civil disobedience is "doomed to fail."
The front-page editorial in the party-run People's Daily, which generally reflects the central government's views, said there is "no room for concessions" on greater democratic reforms.
The editorial was published after Leung ignored a midnight Thursday deadline to step down, instead proposing talks with a top official on resolving the political crisis.
The Occupy movement presents one of the biggest political challenges for Beijing since it violently crushed pro-democracy protests in and around Tiananmen Square in 1989.
Brian Padden contributed to this report from Hong Kong. Some material for this report came from Reuters, AFP and AP.