Oakland police used tear gas and "flash" grenades Saturday to break up hundreds of Occupy protesters after some demonstrators started throwing rocks and flares at officers and tearing down fencing.
Three officers were hurt and 19 people were arrested, the Oakland Police Department said in a release. No details on the officers' injuries were released.
Police said the group started assembling at a downtown plaza Saturday morning, with demonstrators threatening to take over the vacant Henry Kaiser Convention Center. The group then marched through the streets, disrupting traffic.
The crowd grew as the day wore on, with afternoon estimates ranging from about 1,000 to 2,000 people.
The protesters walked to the vacant convention center, where some started tearing down perimeter fencing and "destroying construction equipment" shortly before 3 p.m., the release said.
Police said they issued a dispersal order and used smoke and tear gas after some protesters pelted them with bottles, rocks, burning flares and other objects.
Most of the arrests were made when protesters ignored orders to leave and assaulted officers, the release said. By 4 p.m., the bulk of the crowd had left the convention center and headed back downtown.
The demonstration comes after Occupy protesters said earlier this week that they planned to move into a vacant building and turn it into a social center and political hub. They also threatened to try to shut down the port, occupy the airport and take over City Hall.
In a statement Friday, Oakland City Administrator Deanna Santana said the city would not be "bullied by threats of violence or illegal activity."
Interim police Chief Howard Jordan also warned that officers would arrest those carrying out illegal actions.
Oakland officials said Friday that since the Occupy Oakland encampment was first established in late October, police have arrested about 300 people.
The national Occupy Wall Street movement, which denounces corporate excess and economic inequality, began in New York City in the fall but has been largely dormant lately.
Oakland, New York and Los Angeles were among the cities with the largest and most vocal Occupy protests early on. The demonstrations ebbed after those cities used force to move out hundreds of demonstrators who had set up tent cities.
In Oakland, the police department received heavy criticism for using force to break up earlier protests. Among the critics was the mayor, who said she wasn't briefed on the department's plans. 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.