Police have fired tear gas and arrested more than 100 people as anti-Wall Street protesters tried but failed to take over downtown buildings, including city hall, in Oakland, California.

Protesters from Occupy Oakland -- the local offshoot of Occupy Wall Street -- first targeted the Henry Kaiser convention center Saturday, before proceeding to a YMCA and then city hall, police spokeswoman Johnna Watson said.

"Right now, we're looking at over 100 arrests," Watson told AFP by telephone, adding that three police officers had been injured, police vehicles vandalized and shop windows shattered.

"We will be dealing with this into the evening, for as long as it takes."

Occupy Oakland, ousted from its protest camp in Frank Ogawa Plaza on October 25 amid clashes with police, had earlier announced a weekend "rise up festival" to be held in an unspecified empty building.

"Amazing day," read one entry on Occupy Oakland's Twitter feed (@OccupyOakland) late Saturday. "We didn't get in the building, but fought like our future depended on it. I love u all!"

In a statement earlier Saturday, police said the initial arrests took place when protesters ignored a dispersal order and assaulted officers with rocks and other objects.

The demonstration, which started out peacefully, brought together an estimated 1,000 people, who marched toward the convention center 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.

Police said the crowd began destroying construction equipment and fencing while officers were pelted with bottles, metal pipe, rocks, spray cans and burning flares.

After the marchers were dispersed, about 500 of them regrouped and continued their protest at Frank Ogawa Plaza.

"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.

Protests against inequality and corporate influence on US politics began last September in New York and quickly spread around the country. Most of the demonstrators were removed from the streets at the end of the year.

Meanwhile, in the US capital, protesters from Occupy DC, facing a clampdown on their encampment Monday, stripped down for a topless street party Saturday outside a black-tie gala for Washington's biggest movers and shakers.

President Barack Obama and his wife Michelle topped the guest list for the 99th gathering of the exclusive Alfalfa Club, which convenes once a year in a five-star hotel for a lavish dinner and some witty speech-making.

Outside, up to 200 members of the local offshoot of Occupy Wall Street pogo-danced to Twisted Sister's "We're Not Gonna Take It" and Public Enemy's "Fight the Power" as bemused police officers looked on behind barricades.

Leading the revelers were several young women who gleefully bared their breasts, including one who wrote "freedom of expression" on the belly of another. Several men also stripped to the waist despite the winter chill.