A boy playing cops and robbers with a toy handgun has been shot and wounded by a Los Angeles County sheriffs deputy, officials say.

The boy was shot on Sunday night in Palmdale, north of downtown Los Angeles.

Police Deputy Jeff Gordon said the boy was hospitalised in a stable condition and was expected to survive.

His age and identity were not immediately released.

Gordon said deputies were responding to reports that someone was riding a bicycle and brandishing a handgun.

They spotted the rider and ordered him to drop the weapon but instead he pointed it at the deputies, Gordon said.

One deputy fired a shot and hit the boy in the upper body.