OAKLAND -- Occupy Oakland protesters broke into City Hall, stole an American flag from the City Council chamber and set it on fire Saturday night, punctuating a wild day in which police deployed tear gas, arrested more than 200 marchers and dodged hurling objects.

Demonstrators spent the day trying to break into a convention center and temporarily occupying City Hall and a YMCA, all the while snaking around lines of riot-clad police periodically shooting bean bag projectiles, among other uses of nonlethal force.

Saturday marked the first major clashes between protesters and police since November and left three officers with minor injuries, as protesters threw bottles, metal pipes, rocks, spray cans and "improvised explosive devices," police said.

Late Saturday, paramedics wheeled a pregnant protester away from Frank H. Ogawa Plaza after witnesses said she was hit in the kidney by a police baton. She yelled: "Police did this to me!"

Oakland Mayor Jean Quan spoke moments after the City Hall invasion, saying the city would ask for "stay away" orders against many of the protesters who have repeatedly been arrested in Oakland.

"This particular faction of Occupy ... they're very violent and I'm going to be asking for a lot more mutual aid," Quan said, adding that the weekly marches prevent the city's police force from patrolling other parts of Oakland. "They are hurting the neighborhoods by continuing to do this on Saturday nights."

Police had to ignore 200 lower priority calls for service Saturday night, more than the normal 60 because resources were tied up with the Occupy protests, Sgt. Christopher Bolton said. The first large skirmish of the day took place on the front steps of the Oakland Museum of California. Police arrested 19 marchers during that confrontation.

Later, about 100 protesters were arrested after police ordered them to disperse at the YMCA on Broadway, police said.

The rest of the marchers headed to City Hall, broke into the building and left with at least two American flags, which were quickly burned. Police regained control of the building, arrested more and guarded the trashed lobby.

The protesters walked to the vacant convention center, where some started tearing down perimeter fencing and “destroying construction equipment,” the release said.

Most of the arrests were made when protesters ignored orders to leave and assaulted officers, the release said. An hour later, the bulk of the crowd had left the convention center and headed back downtown.