San Francisco is now under curfew until 5 a.m. local time on Sunday, Mayor London Breed announced in a press conference.
"These are challenging times for our city and in our country," Breed said. "We ask that you follow our direction and support what we're trying to do here to make sure that all of us are safe."
Breed said the California National Guard will remain on stand-by to respond to protests.
Some two dozen other cities across the US have announced curfews for Saturday night into Sunday morning, and more than 10 states have deployed the National Guard.