Story highlights City's police chief says protesters aimed to "further criminal acts, confront police"

He says about 400 have been arrested, while admitting that number "could go up"

3 police officers and 2 protesters are confirmed to have been injured, he says

Oakland City Hall is full of debris and damaged items after protesters got in

Municipal employees in Oakland worked Sunday to clean up damage they said was caused hours earlier by Occupy protesters, about 400 of whom were arrested for breaking into a YMCA and City Hall and challenging police.

Oakland Police Officer Johnna Watson described what transpired as "one of the largest mass arrests that we have seen in the city." Police Chief Howard Jordan said the current estimate of 400 people arrested "could go up."

The police chief accused the protesters of deliberately provoking authorities and flaunting their criminal behavior.

"It became clear that the objective of this crowd was not to peacefully assemble and march, but to seek an opportunity to further criminal acts, confront police and repeatedly attempt to illegally occupy buildings," Jordan told reporters Sunday afternoon.

Mayor Jean Quan took reporters through City Hall on Sunday, pointing to walls where graffiti had already been painted over and other areas of garbage, vandalism and destruction that she said had been left by protesters.

"I ran out of patience a long time ago," Quan said of the Occupy Oakland activists. "We're tired of some people -- and, again, it's a faction of the Occupy movement -- using Oakland as their playground."

"I think people are really angry," she added later, speaking about residents' feelings toward the demonstrators.

Despite the large-scale arrests and their failure to achieve their stated goal of moving into a "large, vacant building" that could be their hub, Occupy Oakland activists remained on the streets Sunday and forged ahead with a planned "Rise Up Festival" at an area park.

Watson, the Oakland police spokeswoman, said Sunday that law enforcement agencies "are preparing for additional problems," including getting help from other agencies and having a large number of officers. Jordan noted that numerous nearby sheriff and city police departments already have provided assistance.

At the same time, Chief Jordan said Sunday that dedicating "personnel and resources ... reduces our ability to focus on public safety priorities." Jordan said that his department received 1,776 calls -- including 482 calls to 911 -- while also tracking the Occupy demonstrators.

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 what activists portray as an out-of-touch corporate, financial and political elite.

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.

Three police officers and two protesters were confirmed wounded in the earlier clashes, the police chief said. He added that two of the officers are believed to be back at work, while the third "remains off on extended injury."

Occupy activists said the number of injuries in their ranks were higher, reporting on the group's Twitter feed that more than a dozen protesters suffered burns and other injuries after being struck by police "flash bang" grenades.

The tensions began to brew early Saturday afternoon when about 250 people gathered in a park across from Oakland City Hall, intent on taking over a previously unidentified building.

Their numbers roughly doubled as they marched through the city, police said. Eventually, the protests turned violent when demonstrators were turned back by police as they tried to break into the long-vacant Henry Kaiser Convention Center.

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 smoke, tear gas and bean-bag bullets. They did so after warning protesters who had begun "destroying construction equipment and fencing" around the Kaiser center, according to a police statement. Officers were "pelted" with bottles, metal pipes, rocks and burning flares, police said.

About 20 people were subsequently arrested, though it did not stop the demonstrators. Scores of them moved to try to take over an occupied, downtown YMCA -- until police forced them out and arrested many of them.

City Hall was another hotbed of activity.

Quan said police have video showing that protesters used a crowbar, or something similar to it, to pry open an emergency door and enter the building. But Omar Yassim, a member of the Occupy group, insisted "the doors were open."

While Yassim said he was not aware of any damage inside City Hall, reporters on Sunday saw that many parts of the building appeared to be in disarray.

That included overturned trash cans, a damaged children's recycled-art exhibit, shattered glass from an interior door, an overturned vending machine, a missing American flag that had been burned and a historic model of City Hall that lay broken on the ground. A large sign reading, "Commune Move In," sat in the hallway.

The mayor said there were no firm estimates as to how much damage had been caused, noting that by midday, workers had already painted over some "obscene" graffiti and that clean-up efforts would continue. Oakland City Administrator Deanna Santana said later that the building should reopen for business Monday.

While saying there is no firm estimate yet on City Hall costs, Quan estimated that demonstrators have inflicted $2 million worth of damage to nearby Frank Ogawa Plaza since October.

"It's like every day we're cleaning graffiti off of City Hall," Quan said. "It is a constant, constant cost.... I want a little restorative justice."

From the beginning, the Occupy Oakland group acknowledged on its website that the action -- touted on its website as "Move-In Day" -- to take over a building that they didn't own 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."

"What we were doing today was civil disobedience," Yassim said.

He described the police response -- which included additional officers brought in nearby counties -- as "despicable."

But while admitting possible issues in the past, Oakland's mayor defended the law enforcement officers more recent actions.

"Yesterday was clearly a constant provocation of the police, and a lot of violence toward them," Quan said Sunday. "And that's not acceptable."