About 300 people were arrested Saturday during a chaotic day of Occupy protests that saw demonstrators break into City Hall and burn an American flag, as police earlier fired tear gas and bean bags to disperse hundreds of people.

Dozens of police officers remained on guard outside City Hall around midnight following the most turbulent day of protests since November, when Oakland police forcefully dismantled an Occupy encampment. An exasperated Mayor Jean Quan, who faced heavy criticism for the police action last fall, called on the Occupy movement to "stop using Oakland as its playground."

"People in the community and people in the Occupy movement have to stop making excuses for this behaviour," Quan said.

Protesters clashed with police throughout the day, at times throwing rocks, bottles and other objects at officers. And police responded by deploying smoke, tear gas and bean bag rounds, City Administrator Deanna Santanta said.

"These demonstrators stated their intention was to provoke officers and engage in illegal activity and that's exactly what has occurred today," Santana said.

Interim Police Chief Howard Jordan said about 300 arrests were made.

Construction equipment destroyed, police say

The group assembled outside City Hall late Saturday morning and marched through the streets, disrupting traffic as they threatened to take over the vacant Henry Kaiser Convention Center.

The protesters walked to the vacant convention centre, where some started tearing down perimetre fencing and "destroying construction equipment" shortly before 3 p.m., police said.

Police said they issued a dispersal order and used smoke and tear gas after some protesters pelted them with bottles, rocks, burning flares and other objects.

Occupy Oakland protestors burn an American flag, which was found inside Oakland City Hall, during a protest on the City Hall steps on Saturday. (Beck Diefenbach/Associated Press)

The number of demonstrators swelled as the day wore on, with afternoon estimates ranging from about 1,000 to 2,000 people.

A majority of the arrests came after police took scores of protesters into custody as they marched through the city's downtown, with some entering a YMCA building, said Sgt. Jeff Thomason, a police spokesman.

Around the same time police were taking people into custody near the YMCA, dozens of officers surrounded City Hall, while others swept the inside of the building looking for protesters who had broken into the building, then ran out of the building with American flags before officers arrived.

'Brutal police response,' protesters allege

The protest group issued an email criticizing police, saying "Occupy Oakland's building occupation, an act of constitutionally protected civil disobedience was disrupted by a brutal police response today."

Michael Davis, 32, who is originally from Ohio and was in the Occupy movement in Cincinnati, said Saturday was a very hectic day that originally started off calm but escalated when police began using "flash bangs, tear gas, smoke grenades and bean bags."

"It was very emotional. I thought it was a very good day for the movement because it brought us back together," Davis said. "We all were here in spirit and everybody actually helped everyone today.

"What could've been handled differently is the way the Oakland police came at us," Davis said. "We were peaceful."

Quan blamed the destruction on a small "very radical, violent" splinter group within Occupy Oakland.

"This is not a situation where we had a 1,000 peaceful people and a few violent people. If you look at what's happening today in terms of destructing property, throwing at and charging the police, it's almost like they are begging for attention and hoping that the police will make an error."