Los Angeles (CNN) -- The video is dramatic: Police in riot gear pursuing crowds of fleeing youths down Hollywood Boulevard.
Fueled by social media, a crowd assembled for an impromptu music block party thrown by a DJ outside a movie premiere turned ugly after being ordered to disperse Wednesday, CNN affiliate KTLA reported. Fist fights broke out, along with confrontations with police. Some members of the crowd threw bottles and others jumped on police cars, smashing windows, the station reported. Los Angeles police officer Karen Rayner told CNN affiliate KCAL that fires were also set.
Authorities resorted to using rubber bullets, batons and bean bag guns to subdue the crowd, and arrested those who still refused to leave, KTLA said.
The Hollywood division of LAPD did not immediately return a call early Thursday from CNN.
KTLA reported the event began about 5 p.m. (8 p.m. ET) when people turned up for the block party after a Twitter post from a DJ calling himself Kaskade. The party was outside the premiere of a movie about the Electric Daisy Carnival, an electronic music festival, at Grauman's Chinese Theatre, KCAL said.
A woman who saw the crowd told KTLA people were blocking traffic and took over the street. Police gave them five minutes to disperse, the woman said -- then returned in riot gear, making arrests as people began fleeing the scene.
By then, KTLA reported, Kaskade was gone. But he took to Twitter, urging members of the crowd to go home. "Everyone chill now!" he wrote. "The block party has officially been shut down! But this is too crazy and we need to be safe!"
Later, he tweeted, "I am really concerned for everyone's safety at this point! Please relax."
"I'm in disbelief," one young woman told KTLA, speaking as she was being handcuffed by police. "I just went to Fresh & Easy (a local grocery store) and bought an energy drink and some candy ... I've never been arrested in my life."
Thursday morning, some on Twitter blamed police for overreacting to the crowd. Others blamed Kaskade. "Next time you want to throw a flash mob dance party, do it in your own neighborhood," one said. Still others pointed to the power of social media.
One poster thanked Kaskade for "giving us our best night ever."
During the incident, police temporarily closed a portion of Hollywood Boulevard, KCAL reported. The street is a major Los Angeles tourist attraction, home to the theatre, Madame Tussaud's wax museum and the Hollywood Walk of Fame. Public transportation in the area was also disrupted temporarily, with some buses detoured, KCAL said.
Kaskade did not have a permit for the gathering, according to KTLA.