Police in riot gear moved in, firing smoke grenades, tear gas and bean-bag projectiles to drive the crowd back.
"Officers were pelted with bottles, metal pipe, rocks, spray cans, improvised explosive devices and burning flares," the Oakland Police Department said in a statement. "Oakland Police Department deployed smoke and tear gas."
Some activists, carrying shields made of plastic garbage cans and corrugated metal, tried to cir vent the police line, and surged toward police on another side of the building as more smoke canisters were fired.
"The City of Oakland welcomes peaceful forms of assembly and freedom of speech, but acts of violence, property destruction and overnight lodging will not be tolerated," police said in a statement.