A pedestrian passes protesters' graffiti in Oakland, Calif., on Sunday, Jan. 29, 2012, following an Occupy Oakland demonstration Saturday. / AP Photo/Noah Berger
Last Updated 4:11 p.m. ET
OAKLAND, Calif. - Oakland officials assessed damage to City Hall caused by Occupy protesters while leaders of the movement claimed Sunday that police acted illegally in arresting hundreds of demonstrators and could face a lawsuit.
Mayor Jean Quan was among those inspecting damage caused after dozens of people broke into City Hall on Saturday, smashing glass display cases, spray-painting graffiti, and burning an American flag.
That break-in culminated a day of clashes between protesters and police. Interim Police Chief Howard Jordan said nearly 400 people were arrested on charges ranging from failure to disperse and vandalism. At least three officers and one protester were injured.
In a news release Sunday, the Occupy Oakland Media Committee criticized the police conduct, saying that most of the arrests were made illegally because police failed to allow protesters to disperse.
"Contrary to their own policy, the OPD gave no option of leaving or instruction on how to depart. These arrests are completely illegal, and this will probably result in another class action lawsuit against the OPD, who have already cost Oakland $58 million in lawsuits over the past 10 years," the release said.
The scene around City Hall was mostly quiet Sunday morning, and it was unclear whether protesters would mount another large-scale demonstration.
Dozens of officers remained present inside and outside City Hall after maintaining guard overnight. Occupy Oakland demonstrators broke into the historic building and burned a U.S. flag, as officers earlier fired tear gas to disperse people throwing rocks and tearing down fencing at a convention center.
"They were never able to occupy a building outside of City Hall," Jordan said Sunday. "We suspect they will try to go to the convention center again. They will get not get in"
Saturday's protests the most turbulent since Oakland police forcefully dismantled an Occupy encampment in November came just days after the group said it planned to use a vacant building as a social center and political hub and threatened to try to shut down the Port of Oakland for a third time, occupy the airport and take over City Hall.
Quan, who faced heavy criticism for the police action last fall, on Saturday 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," Quan said.
On Sunday, Quan said she is tired of the protesters' repeated actions.
"I'm mostly frustrated because it appears that most of them constantly come from outside of Oakland," Quan said. "I think a lot of the young people who come to these demonstrations think they're being revolutionary when they're really hurting the people they claim that they are representing."
Saturday's events began late Saturday morning, when a group assembled outside City Hall and marched through the streets, disrupting traffic as they threatened to take over the vacant Henry Kaiser Convention Center.
The protesters then walked to the convention center, where some started tearing down perimeter 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.
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.
Quan said that at one point, many protesters forced their way into City Hall, where they burned flags, broke an electrical box and damaged several art structures, including a recycled art exhibit created by children.
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.
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."
"What could've been handled differently is the way the Oakland police came at us," Davis said. "We were peaceful."
City leaders joined Quan in criticizing the protesters.
"City Hall is closed for the weekend. There is no excuse for behavior we've witnessed this evening," City Council President Larry Reid said during a news briefing Saturday.
Oakland Councilman Ignacio De La Fuente, echoed Reid's sentiments and said that what was going on amounts to "domestic terrorism."
The national Occupy Wall Street movement, which denounces corporate excess and economic inequality, began in New York City in the fall but has been largely dormant lately.
Oakland, New York and Los Angeles were among the cities with the largest and most vocal Occupy protests early on. The demonstrations ebbed after those cities used force to move out hundreds of demonstrators who had set up tent cities.
In Oakland, the police department received heavy criticism for using force to break up earlier protests. Quan was among the critics, but on Saturday, she seemed to have changed her tune.
"Our officers have been very measured," Quan said. "Were there some mistakes made? There may be. I would say the Oakland police and our allies, so far a small percentage of mistakes. "But quite frankly, a majority of protesters who were charging the police were clearly not being peaceful.
Earlier this month, a court-appointed monitor submitted a report to a federal judge that included "serious concerns" about the department's handling of the Occupy protests.
Jordan said late Saturday that he was in "close contact" with the federal monitor during the protests.
Quan added, "If the demonstrators think that because we are working more closely with the monitor now that we won't do what we have to do to uphold the law and try keep people safe in this city, they're wrong."