Police said they used teargas Occupy Oakland protesters pelted near Lake Merritt and warned them with bottles, rocks, burning flares and other objects
At about 3:45 p.m., the crowd still had not dispersed around the intersection of Jackson Street and 12th Street.
Occupy Oakland protesters say they will gather outside City Hall on Saturday, march to an undisclosed vacant building and commandeer the space as a social center and political headquarters for the movement.
Police have used tear gas and "flash" grenades to break up hundreds of Occupy protesters after some demonstrators started throwing rocks and flares at officers and tearing down fencing.
Police declared the intersection an unlawful assembly area and began running toward protesters with their shields.
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.
The crowd grew as the day wore on, with afternoon estimates ranging from about 1,000 to 2,000 people.
Occupy organizers said the plan today was to go to a vacant building that was to be their new home. Once they reach their destination, organizers had planned to kick off a two-day "Oakland Rise-up Festival" to celebrate the establishment of the movement's new space.
Police were in the process of arresting about 100 Occupy protesters for failing to disperse Saturday night, hours after officers used tear gas on a rowdy group of demonstrators who threw rocks and flares at them and tore down fences.
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 Mayor Jean Quan, 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.
Interim police Chief Howard Jordan also warned that officers would arrest those carrying out illegal actions.
Oakland officials said on Friday that since the Occupy Oakland encampment was first established in late October, police have arrested about 300 people.