(AP) - 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, and police fire tear gas and use "flash" grenades to disperse hundreds of people after some in the crowd threw rocks and bottles and tore down fencing outside a convention center. It was 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 behavior," she said. Authorities say protesters clashed with police throughout the day, at times throwing rocks, bottles and other objects at officers. The protests grew as the day wore on with an estimated 2,000 demonstrators in the streets at one point. Most of the arrests came around 8 p.m., when police took about scores of protesters into custody as they marched through the city's downtown, with some entering a YMCA building, police spokesman Jeff Thomason said. Quan said that at one point, many forced their way into City Hall, where they burned flags, broke into an electrical box and damaged several art structures, including a recycled art exhibit created by children. More help from other police agencies was also sent to Oakland, with busloads of Alameda County sheriff's deputies arriving in the downtown area late Saturday. City Administrator Deanna Santana said protesters pelted officers with bottles, metal pipes, rocks and burning flares and police responded by deploying smoke, tear gas and bean bag rounds. "These demonstrators stated their intention was to provoke officers and engage in illegal activity and that's exactly what has occurred today," Santana said. In a statement Friday, Santana said the city would not be "bullied by threats of violence or illegal activity."