(CNN) -- Occupy protesters broke into Oakland City Hall, damaging displays and burning an American flag, the culmination of protests Saturday that saw police and protesters trade allegations over who was responsible for clashes in the northern California city that ended with the arrest of more than 100 people.
Undeterred, the protesters -- who remained on the street early Sunday morning -- said they will forge ahead with a planned "Rise Up Festival" at an area park later in the day.
Protesters tossed metal pipes, bottles and burning flares at Oakland police, who responded with tear gas, smoke grenades and bean bag bullets.
The clashes started after demonstrators attempted to take over the long-vacant Henry Kaiser Convention Center and turn it into a protest center.
Three police officers and one protester were wounded in the clashes, city and police officials said.
Occupy protesters disputed the report, saying more than a dozen of their group suffered burns and other injuries after being struck by police "flash bang" grenades, according to accounts posted on the group's Twitter feed.
Oakland has been a flash point of the Occupy movement since October when police used tear gas to break up demonstrators who refused to leave downtown. One demonstrator, an Iraq war veteran, suffered a skull fracture after being hit with a police projectile, according to a veteran's group. Police said they acted after the crowd threw paint and other objects at officers.
Occupy Oakland is part of a larger movement that began last year in New York and quickly spread across the globe. While the protesters have highlighted a number of causes, the overarching theme remained the same: populist anger over an out-of-touch corporate, financial and political elite.
The protests are scheduled to continue Sunday with what the group was touting as a "Rise Up Festival" at Oscar Grant Plaza, where protesters have been camping out despite a city ordinance.
The latest tension between Occupy protesters and police began Saturday afternoon when about 250 people gathered in a park across from Oakland City Hall, where they announced plans to take over the convention center.
The protests turned violent when they were turned back by police in their attempt to break into the convention center. By nightfall, the group attempted to take over a YMCA and City Hall.
"It's not a lawful protest by any means," Deputy Police Chief Jeffrey Israel told reporters late Saturday. "They gathered with the intent to break the law."
From the beginning, the group acknowledged on its website that the action -- touted on its website as "Move-In Day" -- to take over the convention center was illegal.
But the group said the move was necessary, in part because "since November, the city of Oakland and its police force have made it impossible for us to meet, to serve food and to provide a place for people to stay."
Omar Yassim called the police response, which included additional officers from nearby counties, "despicable."
"They are shooting rubber bullets at us. We have pictures of people whose clothes were burned by flash bangs," Yassim said.
"What we were doing today was civil disobedience."
But Mayor Jean Quan called the protesters at the center of Saturday's violence a fringe group of the larger Occupy Oakland movement.
"It was really only about 250 people. But they are very violent," she told reporters Saturday night.
She also disputed reports that police were heavy-handed in their response, saying the officers were measured.
"Frankly, the majority of the demonstrators who were clashing with police were not being peaceful," Quan said. "Destruction of property, thing and charging (the police), it's almost as if they are begging for attention. They are hoping the police make an error."
Posts on Occupy Oakland's Twitter feed claim that police met the protesters "with munitions and violence." One read: "#OccupyOakland being teargassed smoked bombed & shot at w rubber bullets."
Oakland police said they used only smoke and tear gas. They did so after warning protesters who had begun "destroying construction equipment and fencing" around the Kaiser center, according to a police statement late Saturday. Officers were "pelted" with bottles, metal pipes, rocks and burning flares, according to another police statement released earlier in the day.
By nightfall, Occupy protesters moved toward Oakland City Hall where police and city officials accused the group of breaking in and vandalizing the building.
Protesters denied breaking into City Hall.
"The doors were open," Yassim said.
But City Administrator Deanna J. Santana said she was told it was a "forced entry" into the building.
Quan said trash cans were overturned, flags in the building were burned, a children's recycled art exhibit was destroyed and a historic model of city hall was overturned.
Yassim said he was not aware of any damage inside the building.
The Oakland Police Department has been under heavy scrutiny since its response to Occupy protests last year.
Elsewhere, the Occupy movement in Washington protested outside the 99th annual Alfalfa Club dinner for high-level dignitaries, including President Barack Obama.
The Washington protest comes two days before the National Park Service is slated to end overnight camping at the Occupy DC sites.
CNN's Greg Morrison contributed to this report.
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