Police in Hong Kong have clashed with pro-democracy protesters as authorities moved in to clear the protest site in the Chinese territory.

Protesters said on Wednesday that the movement's student leaders Joshua Wong and Lester Shum were detained by police a day after arrests of more than 100 demonstrators.

Police wearing helmets and brandishing batons moved in to protect city workers as crowds surged forward to stop them tearing down barricades at the largest part of the Mongkok site.

Tensions were running high the day after police used pepper spray on pro-democracy protesters at the camp, which has been the scene of some of the most violent clashes since the sit-ins began in on September 28.

"If we lose here, we won't lose our heart. We can go somewhere else (to occupy). It doesn't need to be here," Kelvin Ng, a 21-year-old protester, told AFP news agency.

Pro-democracy protesters have been camped out on Hong Kong's streets for almost two months to demand fully free elections for the leadership of the Chinese city.

Police said in a statement they had arrested 116 people, including a 14-year-old boy, after Tuesday's clashes. Twenty police officers were injured, they added.

Workers wearing "I love HK" T-shirts and red baseball caps initially removed barricades blocking the road at the adjacent larger site on Nathan Road on Wednesday, but protesters remained defiant.

"Please obey the injunction, leave immediately," a court bailiff told the crowd before the clearance action.

"I won't leave. It's been illegal from day one with or without the court order," said a protester wearing a yellow helmet and a mask who refused to give his name.

The clearance is the third since the high court in the semi-autonomous Chinese city granted injunctions to let authorities start clearing parts of the protest sites.

It comes as public support wanes for the demonstrators, who are protesting against China's restrictions on who will be allowed to stand in the 2017 elections, and as the movement's leaders are split on the next move.