At least 9 people have been killed in a mass shooting in a city east of Los Angeles following a Lunar New Year celebration that attracted thousands, ABC reported citing police sources.

Sergeant Bob Boese of the Los Angeles County Sheriff’s Department said the shooting occurred at a business on Garvey Avenue in Monterey Park. The suspect is a male, Sgt Boese said. It is unknown if he is in custody.

Officials provided no information for several hours after dozens of police officers had responded to reports of the shooting.

Footage posted on social media showed deserted, cordoned-off streets guarded by police cars.

Seung Won Choi, who owns the Clam House seafood barbecue restaurant across the street from where the shooting happened, told the Los Angeles Times that three people rushed into his business and told him to lock the door.

The people also told Mr Choi that there was a shooter with a semi-automatic weapon who had multiple rounds of ammunition on him so he could reload.

He said he believes the shooting took place at a dance club.

Tens of thousands of people had attended the festival earlier in the day.

Monterey Park is a city of about 60,000 people with a large Asian population around16 kilometres from downtown Los Angeles.

“Our hearts go out to those who lost loved ones tonight in our neighbouring city, Monterey Park, where a mass shooting just occurred,” Los Angeles City Controller Kenneth Mejia said in a tweet.