Demonstrations hit the streets of California for a second night as protesters angered by police killings in Missouri and New York clashed with officers, vandalised businesses and even fought with each other.
The demonstrations were the latest of several in the area around San Francisco - including in Oakland where activism is strong - to protest against recent grand jury decisions in Missouri and New York not to indict white police officers in the deaths of two black men.
Yesterday's protest began peacefully on the University of California, Berkeley, campus but eventually grew rowdy and spilled into Oakland. Activists made their way on to a major road and blocked traffic.
The California Highway Patrol said officers fired tear gas after protesters targeted them with rocks and bottles and tried to set a patrol vehicle on fire. Police also said explosives were thrown at officers, but there was no information immediately available on how potent they were.
As hundreds of protesters began marching through central Berkeley, the unrest that marked protests on Saturday night was touched off again as someone smashed the window of a Radio Shack. When a protester tried to stop growing vandalism, he was hit with a hammer, officer Jennifer Coats said.
Police said groups of protesters began roaming through the city centre area, throwing rubbish bins into streets and setting rubbish on fire, smashing windows on buildings, and damaging and looting businesses. There were also reports of vandalism at City Hall.
Television footage showed protesters smashing windows and breaking into buildings and setting rubbish ablaze.
Ms Coats said police made five arrests in connection with the demonstrations. She said two officers sustained minor injuries on Sunday night.
She said there was "significant damage" to several Berkeley businesses and that many had windows smashed and several shops were looted.
She said the demonstrations had concluded by about 3.30am local time.
Meanwhile, seven people were arrested in Seattle on Saturday night after protesters threw rocks at police and attempted to block a highway.
Politicians on both sides of the aisle have been calling for calm while activists push for police reforms. National Association for the Advancement of Coloured People's president Cornell William Brooks, appearing on the CBS Face The Nation programme, called for outfitting police with body-worn cameras and changing law enforcement policy.
"We have to change the model of policing," Mr Brooks said.