On Twitter, Garcetti quoted Dr. Martin Luther King Jr: "Nonviolence is a powerful & just weapon..It is a sword that heals."
He also urged residents to "exercise 1st Amendment and practice peace in City of Angels tonight."
The LAPD called a citywide tactical alert after demonstrators protesting the not guilty verdict in the George Zimmerman case blocked traffic on the 10 Freeway in the Mid-City area Sunday evening.
Officials said portions of the 10 were closed from 6:20 p.m. to 6:44 p.m. but have since reopened.
Police emphasized that most of the protesters were peaceful. But there have been several splinter groups from the main protest that have been more aggressive, officials said.
LAPD Cmdr. Andy Smith said some demonstrators threw rocks and D-cell batteries at police near the corner of Washington Boulevard and 10th Avenue. Police responded by firing less-than-lethal rounds at the demonstrators.
So far only one arrest has been made.
As of 9:30 p.m., there were still protests going along Crenshaw Boulevard as well as on La Brea Avenue. On La Brea, a group of less than 100 demonstrators marched through the Fairfax District and into Hollywood. Witnesses said they stopped at the intersection with Santa Monica Boulevard, where they were holding a sit-in.
About 150 protesters remained late Sunday at the intersection of Crenshaw Boulevard and Coliseum Street, occasionally disrupting traffic. Dozens of police in riot gear stood nearby as demonstrators chanted “Justice for Trayvon!”
Then shortly after 9 p.m., police cleared out to cheers from the crowd, and about 40 people swarmed onto Crenshaw Boulevard to block traffic. Police immediately returned to the scene.
More than 200 protesters gathered in Leimert Park Sunday evening engaged police in a brief standoff. The protesters surrounded at least three patrol cars and repeatedly chanted “Trayvon Martin!” as the officers got out of their cars looking tense but not taking any action.
About a dozen more officers in riot gear stood by about a block away. Some protesters chanted epithets at the officers.
“I think they should just leave,” said one man. “No one asked them to be here. It’s a peaceful demonstration…The police are just going to provoke something by just being here.”
After about 10 minutes, the demonstrators let the officers drive through the crowd. All of the police eventually left the scene and the demonstration continued peacefully.
As tourists looked on, the protesters chanted: “What do we want?” “Justice!” “When do we want it?” “Now!” The demonstration was one of many in major U.S. cities Sunday after neighborhood watch volunteer George Zimmerman was acquitted Saturday night in the 2012 death of Trayvon Martin in Florida.