|Demonstrators shielded themselves as police fired projectiles and chemicals during a confrontation [Reuters]
Police have fired tear gas and flash grenades while arresting more than 300 people as anti-Wall Street protesters tried but failed to take over downtown buildings, including the city hall, in Oakland, California.
Protesters from Occupy Oakland - the local offshoot of Occupy Wall Street - first targeted the empty Henry J Kaiser convention center on Saturday, before trying to take over the city hall, but were forcibly removed from each area by police.
Police spokesperson Johnna Watson told the AFP news agency that throughout the day's events three police officers had been injured, police vehicles vandalised and shop windows shattered. "We will be dealing with this into the evening, for as long as it takes," she said.
The bulk of arrests occurred in one incident when protesters were kettled by police into a city block.
Activists told Al Jazeera that they 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.
The Oakland Police Department already faces numerous lawsuits for excessive force during protests, including for a mass arrest incident in late 2010 in which 148 people were arrested "unconstitutionally", according to the lawsuit.
Occupy Oakland had earlier announced a weekend "rise up festival" to be held in an unspecified empty building.
It threatened the city, saying that activists would indefinitely shut down the airport, stop business at the port and take over city hall, if the city would not allow them to move into a building as planned.
The protest group had been ousted for the first time from its camp in a park outside the city hall building on October 25 after clashes with police, but has maintained regular protests ever since.
"Amazing day," read one entry on Occupy Oakland's Twitter feed late on Saturday. "We didnt get in the building, but fought like our future depended on it."
'Improvised explosive devices'
In a statement from earlier on Saturday, police said the initial arrests took place when protesters ignored a dispersal order and assaulted officers with rocks and other objects.
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The demonstration, which started out peacefully, brought together an estimated 2,000 people, who marched towards the convention centre that includes a 5,500-seat arena, theater and event spaces.
Once there, several protesters tried to tear down a fence and occupy the building, according to media reports.
The police press release stated that the crowd "charged a skirmish line at Oak Street and pelted officers with bottles, metal pipe, rocks, spray cans, improvised explosive devices and burning flares".
After the marchers were dispersed, about 500 of them regrouped and continued their protest at the city centre plaza, where some burned an American flag on the city hall steps and tried to take over the building.
"If the cops are willing to defend property over people, I think that shows where the city's priorities are," said Carla Orendorff, a student at University of California Davis.
'Stop using Oakland'
After incidents ended on Saturday night, Occupy Oakland activists vowed to return to the streets and attempt to take over another vacant building on Sunday.
Saturday was the most turbulent day of protests in Oakland since November, when police forcefully dismantled an Occupy encampment.
Oakland was among the cities with the largest and most vocal Occupy protests early on. The city came into the spotlight after police used force to move out hundreds of demonstrators who had set up tents outside city hall.
An exasperated Mayor Jean Quan, who faced heavy criticism for the police action last autumn, then called on the Occupy movement to "stop using Oakland as its playground".
The Occupy protests against inequality and corporate influence on US politics began last September in New York and quickly spread around the country.
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.