Local residents are expressing their shock after a mass shooting in Monterey Park, California, that left at least 10 people dead and at least 10 others wounded.

The incident on Saturday night happened as thousands were gathered downtown in the majority Asian-American city to mark the Lunar New Year state holiday.

The gunman is said to have entered Star Ballroom Dance Studio, a popular club, and fired multiple rounds at patrons before fleeing the scene.

Wong Wei told the Los Angeles Times that his friend was at the club but had been in the bathroom when the shooting began.

He said that when she came out, she saw the gunman firing indiscriminately from a long gun, and she also saw three people lying dead, including a boss of the club. She escaped to Mr Wei's nearby home, he said.