Californian police made 25 arrests on Monday as protesters chained themselves to the doors of the Oakland police headquarters.

Demonstrators blocked streets around the building and chained shut four doors to protest against recent grand jury decisions not to indict white police officers who killed unarmed black men in Ferguson, Missouri, and New York.

Protesters in front of one entrance held a sign reading “End the War on Black People.”

Television reports showed about a dozen people blocking roads near the police building.

One protester climbed a flagpole (pictured).

Police estimated the number of protesters at between 150 and 200 and said at least some of those blocking roads were chained to each other.

Oakland and Berkeley have seen numerous protests since grand juries recently declined to indict white officers in the fatal shooting of 18-year-old Michael Brown in Ferguson and the chokehold death of Eric Garner in New York.