Police in riot gear clashed with protesters in Oakland in the early morning hours on Thursday, firing tear gas to disperse demonstrators lingering in the streets after a day of mostly peaceful rallies against economic inequality and police brutality.
The confrontation, which erupted after midnight, appeared aimed at preventing the protesters from expanding their foothold in the streets around a public plaza that has become a hub for demonstrations in the northern California city.
More than 200 officers, some of them ferried in aboard buses, lined up shoulder to shoulder and donned gas masks, then declared the crowd to be an unlawful assembly and fired volleys of tear gas as protesters turned and ran.
A few activists paused to pick up canisters and hurl them back at officers as they fled, while others threw rocks.
This was peaceful until you came! protesters shouted at police. Police later charged the plaza with batons and more tear gas to push protesters farther into centre of the square.
The clashes in Oakland, which shot to the forefront of nationwide anti-Wall Street protests after a former Marine was badly injured in a rally last week, followed a day of rallies that drew some 5,000 activists at their peak and shuttered the busy Port of Oakland but failed to shut down the city.
At least one protester was carried away with an injury to his leg, and another who had been placed under arrest, his hands cuffed behind his back, lay on the ground with blood streaming down his face.
About three dozen activists were arrested, lined up seated along a street curb in plastic wrist restraints as they waited to be taken away by police.
The anti-Wall Street activists, who complain bitterly about a financial system they believe benefits mainly corporations and the wealthy, had aimed to disrupt commerce with a special focus on banks and other symbols of corporate America.
The clash with police turned into a tense stand-off as most of the protesters retreated to Frank Ogawa Plaza, the large outdoor square next to City Hall that has been a hub of the so-called Occupy Oakland movement.
Police, meanwhile, formed a cordon along the northern perimeter of the plaza about a block or two from its edge. Other officers branched off towards other pockets of protesters outside the plaza.
Many of the street lights in the area suddenly went dark as the confrontation unfolded, but it was not clear whether they were turned off or knocked out by a power disruption.
On Wednesday evening, an official said maritime operations at the Oakland port, which handles about $39 billion a year in imports and exports, had been effectively shut down.
Protesters, who streamed across a freeway overpass to gather in front of the port gates, stood atop tractor-trailers stopped in the middle of the street.
Others climbed onto scaffolding over railroad tracks as a band played a version of the Led Zeppelin song Whole Lotta Love, using amplifiers powered by stationary bike generators.
Maritime area operations will resume when it is safe and secure to do so, the port said in a statement. A port spokesman said officials hoped to reopen the facility on Thursday morning.
The atmosphere at the protests turned tense well before police moved after when a protester was apparently struck by a car in downtown Oakland. Acting Oakland Police Chief Howard Jordan later said the pedestrian was taken to a local hospital for treatment of non-life-threatening injuries.
Small groups were later seen in local TV images running through the streets, trying to start small trash fires or climbing on top of moving television news vans.
Windows were smashed at several Oakland banks and a Whole Foods market, with pictures of the damage posted on Twitter. Jordan blamed the vandalism and unruliness on a small group he identified as anarchists.
The demonstrations centered at Ogawa Plaza, scene of a tug-of-war last week between police who cleared an Occupy Oakland encampment there and protesters who sought to return, and ultimately succeeded in doing so.
Prior to marching on the port, protesters blocked the downtown intersection of 14th Street and Broadway, where Iraq war veteran Scott Olsen was wounded during a clash with police on the night of October 25.
It was the wounding of Olsen, a former Marine turned peace activist who suffered a serious head injury during protests last week, that seemed to galvanize protesters and broadened their complaints to include police brutality.
Olsen remains in an Oakland hospital in fair condition.
Protest organizers say Olsen, 24, was struck by a tear gas canister fired by police. Jordan opened an investigation into the incident but has not said how he believes Olsen was hurt.
(Additional reporting by Dan Whitcomb, Mary Slosson, Steve Gorman, Emmett Berg, Matthew Ward, Bill Rigby and R.T. Watson; Writing by Dan Whitcomb; Editing by Jerry Norton, Cynthia Johnston and Todd Eastham)