Protesters block roads by Oakland police building (w/video)

OAKLAND — Demonstrators blocked streets around Oakland police headquarters and chained shut four of the building's doors Monday to protest recent grand jury decisions not to indict white officers who killed unarmed black men in Ferguson, Missouri, and New York.

Police made 25 arrests as the protesters also chained themselves to the doors and prevented people from getting inside. The city and nearby Berkeley have been a hotbed for protests against police in recent weeks.

Demonstrators in front of one entrance held a sign that read, "End the War on Black People."

"It's not OK; black lives matter," Gopal Dayeneni, one of the protesters, told KTVU-TV.

Television news footage showed about a dozen people blocking two roads off Interstate 880 in downtown Oakland near the police building. They were among those arrested, police said. One protester climbed a flagpole, but then came down.

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

Later Monday, about 150 high school students in Oakland marched in the East Bay city and a smaller group held a candlelight vigil at Lake Merritt. Both demonstrations were peaceful, Oakland police said.

Oakland and neighboring Berkeley have seen numerous protests — some violent — since grand juries recently declined to indict white officers in the fatal shooting of 18-year-old Michael Brown in Ferguson, Missouri, and the chokehold death of Eric Garner in New York City. Both men were black and unarmed.

Monday's protest in Oakland came a night after Brown's father visited a San Francisco church to thank those who supported his family, and after artists claimed responsibility for hanging three cardboard images of black lynching victims at a Northern California university. A note posted at the University of California, Berkeley, said the effigies were meant to provoke thought about a systemic history of violence against blacks.

Campus authorities said Monday they no longer view the life-size effigies as a hate crime.