Multiple protesters denouncing the George Zimmerman verdict were taken into custody Monday night  after Los Angeles police declared an unlawful assembly in the Crenshaw district. 

The police actions came after several hours of lawlessness along Crenshaw Boulevard and adjacent streets as groups of youths stomped on cars, assaulted bystanders, set fires and vandalized property, authorities said. 

Protesters hurled several chunks of concrete at officers on Vernon Avenue, the Los Angeles Police Department said. No injuries were reported.

Late Monday, a number of streets in the area had been cleared. The LAPD declared an unlawful assembly shortly before 10 p.m.

The chaos created a nightmare for area commuters as cars were trapped around Leimert Park and bus service was cancelled on Crenshaw and Martin Luther King Jr. boulevards, Metro said. 

Earlier Monday, several protesters made their way into a Wal-Mart on Crenshaw Boulevard as guards scrambled to close security gates. A short time later, Los Angeles Police Department officers wearing helmets and carrying batons swarmed the store as others marched through the parking lot.

The LAPD declared a tactical alert about 9 p.m., which means that off-duty officers could be held on duty when their shifts end and may respond only to high-priority calls.

"We want to support everyone's 1st Amendment right to protest, but we also want to ensure public safety and not allow people to commit violent acts," Cmdr. Andy Smith told The Times.

Police estimated that up to 150 people were engaged in lawless activity along Crenshaw as they jumped on top of vehicles and appeared to assault bystanders.

Some protesters ignited fireworks in the middle of Crenshaw. The evening began with a peaceful vigil at Leimert Park. But groups of youths broke off and began engaging in lawlessness along Crenshaw Boulevard.

PHOTOS: Trayvon Martin and George Zimmerman: The controversial case

Zimmerman, 29, a neighborhood watch volunteer, was acquitted Saturday in Florida of second-degree murder and manslaughter in the 2012 shooting death of Trayvon Martin, 17.

The verdict has sparked protests across the country and led to arrests and protests.

Earlier Monday in Oakland, hundreds of protesters stormed Interstate 880 near downtown and blocked traffic in southbound and northbound lanes. The protesters were cleared from the freeway and made their way downtown, authorities said.

By late Monday night, multiple arrests had been made in the downtown area as officers from neighboring jurisdictions responded to the chaos, the Oakland Police Department said.

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Twitter: @LAJourno

robert.lopez@latimes.com