25 protesters arrested for blocking Oakland police headquarters

OAKLAND, Calif. -- Police arrested 25 protesters who blocked the Oakland Police Department headquarters and nearby streets to call for the end of police killings of unarmed black people.

Oakland police told ABC News affiliate KGO-TV that there were no permits issued for Monday morning's action and that it came as a surprise to city planners and law enforcement.

Officers arrested at least 13 people who had chained themselves to the entrances of the police building around 7:30 a.m.

Police say the glass door to one entrance was broken by police tools while officers cut the protesters free.

Some activists also blocked nearby streets and locked themselves together with PVC pipes.

A protester also climbed up the flagpole at police headquarters to put up a flag that said "black lives matter," which also depicted the faces of black men killed by police.

As Oakland enters its fourth week of protests following a grand jury's decision not to indict Ferguson, Missouri, police Officer Darren Wilson for shooting and killing black 18-year-old Michael Brown, organizer Cat Brooks said demonstrators had finally reached Oakland police headquarters.

Monday's action was organized by black leadership, including the groups BlackOut Collective, Onyx, Black Lives Matter and Black Brunch, which had previously organized actions that shut down the West Oakland BART station and marches through Oakland's Rockridge neighborhood.

KGO-TV contributed to this report.