Several journalists were injured by officers during protests in Berkeley over police killings in Missouri and New York, according to a media organization.
In an open letter to Berkeley Police Chief Michael Meehan and Mayor Tom Bates, the Society of Professional Journalists' Northern California Chapter called for an investigation into "inappropriate use of force" on members of the media during protests Saturday.
"We are sure that you agree attacks on journalists are entirely unacceptable," the letter said. "Reporters are on scene to report the news as it happens. They are not participants in the protests. Under no circumstances should members of the press be subject to such gratuitous and potentially deadly police violence."
The organization condemned the officers' conduct, calling it outrageous.
Journalists reported that they were struck with police batons, even though they were clearly displaying their credentials, according to the letter.
A news photographer told the organization that he was struck by an officer even after he showed him his credential and told him who he was.
Another reporter suffered "'serious blows" from police who "hit him with impunity." Several journalists told the organization that a news photographer was struck on head with a baton.
Other protesters, who are not members of the media, also reported they were hit by police during the protests.
Cindy Pincus, an intern minister at First Unitarian Universalist Society of San Francisco, said the back of her head was struck by a police baton while she was retreating during the protests Sunday.
She tweeted a graphic photograph of the back of her bloodied head.
Calls and emails to Berkeley police have not been returned.
"Thank you to all the members of the community that have supported us through this difficult period of unrest," Berkeley police said on Facebook. "We are on the skirmish line protecting your homes, families and rights, and proud to do so."
But according the California Highway Patrol, eight "aggressive protesters" on California 24 were arrested after they threw rocks and bottles at officers who were trying to clear them from the highway.
CHP said two officers were injured and five patrol cars were vandalized after a crowd of 500 to 600 protesters marched through downtown Berkeley.
Protesters smashed the window of a Radio Shack store. A man in the crowd tried to stop them and was struck by a hammer, authorities said.
Police used tear gas to disperse the crowd, authorities said.
It was the second consecutive night of protests that turned violent, resulting in arrests and injuries. Protesters returned to the streets Monday night, but there were no immediate reports of injuries or arrests.