Crews spent Sunday cleaning up following Saturday's demonstration - the most convulsive since Oakland police forcefully dismantled an Occupy encampment in November.
Authorities said some of the protesters broke into City Hall. They smashed glass, spray-painted walls and burned an American flag.
At least three officers and one demonstrator were hurt. People were arrested on charges ranging from failure to disperse to vandalism. The protesters claim they were not given clear orders to disperse.
The protests came just days after the announcement of a new round of actions. The group said it planned to use a vacant building as a social center and political hub and threatened to try to shut down the Port of Oakland for a third time, occupy the airport and take over City Hall.
Demonstrations in Oakland have cost the financially troubled city about $5 million.
Meantime, Los Angeles protesters hit the streets to show solidarity with Oakland demonstrators. About 100 people marched from MacArthur Park to the Rampart police station Sunday night.
Police said there were no major confrontations, and the crowd eventually dispersed without any arrests being made.
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.
The Associated Press contributed to this report.
