Police in Oakland have made one of the largest mass arrests of Occupy activists, detaining some 400 people in the latest attempt to disperse protesters gathered in the centre of the northern California city.
As a clean-up crew worked to undo the damage inflicted on Saturday night, Oakland police and city officials told a press conference on Sunday they did not have a final tally of arrests which were made on charges ranging from failure to disperse to vandalism.
The bulk of arrests occurred in one incident when protesters were kettled by police into a city block. Activists told Al Jazeera that they had entered the YMCA building on that street in order to find an escape from arrest.
Some managed to escape through back doors before police entered and detained those who were left.
Earlier on Sunday, the West Coast city's emergency operations office put the arrest figure at around 400 after skirmishes had left three officers and at least one demonstrator injured.
"While City Hall sustained damage, we anticipate that all city offices will be open for regular business tomorrow [Monday]."
- Deanna Santana, Oakland city administrator
Though Saturday's events started peacefully, by the afternoon the scene had deteriorated into clashes punctuated by rock and bottle throwing by protesters and volleys of tear gas from police.
Police said a group of protesters burned an American flag in front of City Hall, then entered the building and destroyed a vending machine, light fixtures and a historic scale model of the edifice. The city's 911 emergency system was overwhelmed during the disturbances.
"While City Hall sustained damage, we anticipate that all city offices will be open for regular business tomorrow," said Deanna Santana, Oakland's city administrator.
Saturday's protests, the most turbulent since Oakland police forcefully dismantled an Occupy encampment in November, came just days after the announcement of a separate new round of activist actions.
The group has vowed to keep up its protest activities to bring attention to economic inequality and said it planned to use a vacant building as a social centre and political hub, shut down the Port of Oakland for a third time, "occupy" the airport and take over City Hall.
After the arrests, the Occupy Oakland Media Committee criticised the police's conduct, saying most of the arrests were made illegally because police failed to allow protesters to disperse. It promised legal retaliation.
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"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,'' a press release from the group said.
Oakland has become a flashpoint for the national Occupy protests that began last year in New York's financial district and spread to dozens of cities.
The protests in most cities have been peaceful and sparked a national debate over how much of the country's wealth is held by the richest one per cent of the population - a point President Barack Obama has sought to capitalise on by calling for higher taxes on the most affluent Americans.
Occupy protests focused on Oakland after an Iraq war veteran, Scott Olsen, was critically injured during a demonstration in October.
Protesters said he was hit in the head by a tear gas canister but authorities have never said exactly how he was hurt.
The Occupy movement appeared to have lost momentum late last year as police cleared protest camps in several cities and local media came under scrutiny for not covering the domestic protests adequately.
Tension also flared on Sunday in Washington, where police used a taser on an Occupy protester during an arrest at a park near the White House, police said.
The National Park Service says it will begin enforcing a ban on Occupy protesters camping overnight in McPherson Square and Freedom Plaza, two parks near the White House where they have been living since October.
That order, if carried out as promised starting at noon on Monday, could be a blow to one of the highest-profile chapters of the movement.