At least 12 people and six officers were injured during the clashes, district commander Kwok Pak-chung said at a pre-dawn press briefing.
Protest leaders called off planned talks with the government on political reforms after the battles kicked off yesterday afternoon in gritty, blue-collar Mong Kok, across Victoria Harbor from the activists' main protest camp. Police struggled for hours to control the battles as attackers pushed, shoved and jeered the protesters.
Those arrested face charges of unlawful assembly, fighting in public and assault, Kwok said, adding that eight men are believed to have backgrounds involving triads, or organized crime gangs. The protesters urged residents to join their cause and demanded that the police protect their encampments.
The Hong Kong Federation of Students, one of the groups leading the demonstrations that drew tens of thousands of people earlier this week, said they saw no choice but to cancel the dialogue.
The government is demanding the streets be cleared
"The government is demanding the streets be cleared. We call upon all Hong Kong people to immediately come to protect our positions and fight to the end," the group said in a statement.
They demanded the government hold someone responsible for the scuffles yesterday, the worst disturbances since police used tear gas and pepper spray on protesters last weekend to try to disperse them.
Hundreds of people remained in the streets early today in Mong Kok, one of Hong Kong's busiest shopping areas, after the clashes. "Of course I'm scared, but we have to stay and support everyone," said Michael Yipu, 28, who works in a bank.
Well after midnight, the crowds stood peacefully, occasionally chanting and shouting, while police looked on.
The standoff is the biggest challenge to Beijing's authority since it took over the former British colony in 1997. Earlier yesterday, the students had agreed to talks with the government proposed by Hong Kong's leader, Chief Executive Leung Chun-ying.
But his attempt to defuse tensions fell flat as many protesters were unhappy with his refusal to yield their demands for his resignation.
The cancellation of the talks prompted by clashes with men who tried to tear down the makeshift barricades and tents set up by the demonstrators left the next steps in the crisis uncertain.