Protesters set up camp on top of the Oakland Police Department building on Thursday.
Several hundred people gathered outside the department building to demand justice for Michael Brown, the unarmed black 18-year-old killed by a white police officer in Ferguson, Missouri.
In Oakland, where protesters are rallying in solidarity with Brown, about a dozen protesters were arrested and police deployed pepper spray, rubber bullets and water cannons.
One man was arrested after he was arrested by police for blocking traffic on a freeway.
The protests came as Trump, who has criticized the Black Lives Matter movement and condemned the protests as a political stunt, made a new appearance at the police department.
Trump arrived Thursday at a downtown Oakland police station and addressed the crowd, telling them that his administration is taking a very different stance on the Black lives matter movement than the Obama administration.
He also condemned what he called “violence, chaos and destruction” by protesters.
“We have no tolerance for violence,” Trump said.
“It is unacceptable.
It is not who we are as a country.
We are a country that values human life, it values people and it values peace and it has a message that has to be heard and I will not be silenced.”
Earlier in the day, Trump met with the head of the American Civil Liberties Union and called on the police to get back to protecting their communities.
In an interview with ABC News on Thursday, he said he would send in the National Guard to the streets of cities that had refused to cooperate with the Justice Department’s probe into the police killing of Brown.
The Trump administration has said the Justice department’s probe of the police shooting of Brown was politically motivated and that it is seeking to indict the officers involved.
Follow AP coverage of the protests: AP: Protesters hold rally outside Oakland police department article Protesters at the Oakland police agency say they have staged a “day of action” to demand a thorough investigation of the shooting death of Michael Brown.
A handful of protesters surrounded the Oakland City Hall building where the department’s acting police chief is based and gathered Thursday.
A number of people wore red “black lives matter” T-shirts with the slogan “peace is our message.”
The protesters chanted slogans such as “Justice for Michael” and “Black lives matter.”
Protesters are staging a “Day of Action” on Friday, calling on the city to conduct an independent investigation into the shooting.
Protesters were met with pepper spray and water cannon, but there was no immediate response from Oakland Police.
Police said in a statement that the protesters are “threatening law enforcement officers, disrupting traffic, obstructing police officers, obstruct[ing] emergency vehicles, and disrupting law enforcement and community relations.”
The protesters have set up a makeshift memorial to Brown, who was shot and killed by Officer Darren Wilson in August.
The police department is investigating Wilson’s death.
A white man was also killed by police officers in Oakland in January, but no charges were filed in the case.
The officer involved in that case, who is black, was charged with felony murder and other offenses.