The group started filling streets about 8:40 p.m. PDT Thursday, prompting police to respond to the scene.
Los Angeles Police Department spokeswoman Karen Rayner said some protesters began throwing rocks, bottles and other objects at officers, and police were on citywide tactical alert.
She said there were several arrests and at least one officer injured, but she had no further details.
Police had dispersed the crowd before midnight.
Rayner said police believe at least some of the protesters were associated with the Occupy Los Angeles movement, but that has not been confirmed.
The Los Angeles Times reported that a woman who identified herself as part of the Occupy movement said protesters attended the monthly event with the intention of showing support for people previously arrested for chalking on the sidewalk.
"We were handing out free chalk for freedom of speech," said Cheryl Aichele, 34.
City News Service reported that several people suffered skin welts they claimed resulted from clashes with police.