LOS ANGELES – Los Angeles Mayor Eric Garcetti said violence and vandalism in city streets resulted in 13 arrests in protests over George Zimmerman's Florida acquittal in the shooting death of Trayvon Martin.
Speaking at a news conference with Garcetti late Monday, LAPD Chief Charlie Beck said about 150 people broke off from a larger, peaceful protest and began walking through the streets, committing multiple acts of vandalism and several assaults.
The officials didn't elaborate on the assaults or any potential injuries.
Beck said more than 300 officers were called to the scene. They were slow to directly engage the protesters in an attempt to allow a peaceful end to the demonstration.
He said police would take a much stricter posture if the protests continued for another night.
Protesters ran through Los Angeles streets, stopping traffic, breaking windows and at one point raiding a Wal-Mart store, and a major freeway was blocked in the San Francisco Bay Area in the third night of protests in California over George Zimmerman's Florida acquittal in the shooting death of Trayvon Martin.
Several hundred mostly peaceful protesters gathered Monday night at Leimert Park southwest of downtown Los Angeles, many of them chanting, praying and singing.
But a smaller group of about 100 people splintered off and began blocking traffic on nearby Crenshaw Boulevard, some of them jumping on cars and breaking windows.
At about 10 p.m., a few hours after the splinter protest began, police declared the group an unlawful assembly, and many in the crowd began to disperse.
Several protesters ran into a Wal-Mart store, where they knocked down displays before store security chased them out, and police began guarding the door.
TV news helicopters showed some people apparently throwing punches along the street. There were no immediate reports of injuries.
"I commend the prayer rally attendees in Leimert Park for practicing peace," tweeted LA Mayor Eric Garcetti, who returned early from an East Coast visit. "I call on people in street on Crenshaw to follow their example."
In Oakland, dozens of demonstrators briefly blocked all lanes of Interstate 880 at the tail end of rush hour Monday evening, stopping traffic in both directions for several minutes before they were cleared by authorities. Several protesters laid their bicycles on the ground in front of stopped cars.
"You've got to go. You will go to jail," one police officer shouted at demonstrators who were blocking traffic, the Oakland Tribune reported. However, police decided not to make arrests as the marchers, chanting "Justice for Trayvon Martin," were directed back to surface streets.
Later, another group tried to march up the onramp to Interstate 580 before being turned away by Oakland police and California Highway Patrol officers.
The freeway protesters broke off from a larger group organized via social media that gathered at Oakland City Hall about an hour earlier. Several people were arrested for acts of violence and vandalism while marching from City Hall, authorities said.
Over the weekend, demonstrators in Oakland and Los Angeles blocked traffic and clashed with police in protests over a Florida jury's acquittal of neighborhood watch volunteer Zimmerman in the shooting death of the unarmed black teenager.
Police shot beanbag rounds and arrested six people -- including one on suspicion of assaulting an officer -- while breaking up relatively small demonstrations before dawn.
No injuries were reported to either demonstrators or officers.
Most demonstrations around the state were peaceful.
Democratic Sen. Barbara Boxer sent a letter Monday to U.S. Attorney General Eric Holder supporting the Justice Department decision to review the case to determine whether Martin's civil rights were violated.
"I respect the fact that the jury has spoken ... but I don't think this should be the last word," Boxer wrote in the letter.
"Trayvon Martin's death was a tragedy and has raised many sensitive and important issues," she wrote. "We should explore every avenue in an effort to ensure that something like this never happens again."