Despite a massive Los Angeles police presence Thursday night, sporadic violence broke out near Staples Center after the Lakers defeated the Boston Celtics in the NBA Finals.

Crowds hurled bottles and other objects at police, smashed marquees, jumped on vehicles, broke windows, and set rubbish dumpsters and vehicles on fire along Figueroa Street north of Staples Center and on Flower Street.

Police fired non-lethal rounds to disperse the crowd at Figueroa and Venice Boulevard after several small fires were set, as well as at 11th and Hope streets. At 7th and Flower, a car believed to be a taxicab was engulfed in flames.

At least one person was beaten unconscious as fights broke out on Flower Street near Olympic Boulevard. A bicyclist was injured when struck by a Los Angeles County Sheriff's Department vehicle near 11th and Flower streets, according to the LAPD.

In all, there were multiple injuries but no loss of life, officials said. One police officer suffered a broken nose. As night wore on, fire crews responded to many rubbish fires and some vehicle fires, according to the Los Angeles Fire Department.

The LAPD declared an unlawful assembly moments after the game ended.

Hundreds of officers in patrol cars, on foot and on horseback moved in to clear streets and break up the crowds. At least 12 people were arrested for crimes including public drunkenness, vandalism and inciting a riot. One person was arrested for assault on a police officer, authorities said.

Several dozen people rushed onto the 10 Freeway near Figueroa and Washington boulevards, disrupting traffic, the California Highway Patrol said.

At 8th and Figueroa, Lakers fans and a phalanx of more than two dozen police, wearing riot gear and wielding batons, faced off. The stand-off began when a bunch of fans tore down a traffic sign and then ripped out two newspaper stands and lighted the papers on fire. When the police marched up Figueroa, about two dozen abreast, the crowd slowly receded. Some people were throwing energy drinks, which had been passed out for free after the win. Others posed for photos in front of the line of police.

A group of overzealous fans began smashing the windows of a black Honda and trying to turn it over. Others protested the violence: "You isn't from L.A.! This is L.A. No burning!" one person in a Kobe Bryant jersey shouted.