Police in riot gear clashed with protesters in Oakland 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 largely working-class city on the eastern banks of San Francisco Bay.
More than 200 officers, some ferried downtown 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. One barricade was set ablaze after the police first advanced.
"This was peaceful until you came!" some protesters shouted at police. Police later charged toward protesters with batons and more tear gas to push them farther into center of the square, where activists have reassembled a make-shift encampment forcibly dismantled by authorities last week.
The latest unrest in Oakland, which shot to the forefront of nationwide anti-Wall Street protests after a former Marine was badly injured in last week's clashes, followed a day of rallies that drew some 5,000 activists at their peak and shuttered the busy Port of Oakland but failed to grind the city to a halt.
At least one protester was carried away with an injury to his leg. Another who had been arrested, his hands bound behind him, lay on the ground with blood streaming down his face.
Police estimated around 60 protesters had been arrested. Dozens of them were lined up seated along a street curb in plastic wrist restraints as they waited to be taken away.
One of them, Adam Konner, 29, of Ann Arbor, Michigan, said he heard a police announcement ordering "campers to move back to your tents," before police advanced again.
"I was trying to figure what they were saying. I was trying to figure out if I could go back into the plaza," he told Reuters. He said he was suddenly confronted by police who knocked him to the ground and placed him under arrest.
The anti-Wall Street activists, protesting a financial system they believe benefits mainly corporations and the wealthy, had set out on Wednesday to disrupt commerce with a focus on banks and other symbols of corporate America.
But a police force that had largely kept its distance during the day ended up in a tense stand-off as most of the protesters had retreated to Frank Ogawa Plaza, the large outdoor square next to City Hall that has been the fulcrum of the so-called Occupy Oakland movement.
One officer at the scene, who declined to be named, told Reuters police had no plans to clear the encampment for the moment.
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, had 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 in 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 fires or climbing on top of moving television news vans.
At one point, several people appeared to force open the driver's-side door of a news van, but after a few tense moments the door closed again and the van drove away safely.
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 Frank 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.
Protesters, prior to marching on the port, had also blocked the downtown intersection of 14th street and Broadway, where ex-Marine 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.
He 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 and Cynthia Johnston)