Two wildfires that erupted and spread quickly in southern California have destroyed dozens of homes and forced evacuations in remote areas of the US state's Kern County.

The most destructive of the fires was burning about 10 miles southeast of Tehachapi, a city located in a mountainous area between Bakersfield and Mojave.

More than 30 homes were lost in the small hill community of Old West Ranch and another 150 structures were threatened, firefighters said on Tuesday.

The area is about 70 miles north of Los Angeles.

Kern County Fire Department Engineer Anthony Romero said the fire erupted at about 3 pm and quickly grew to more than 500 acres.

About 200 firefighters were on the scene, along with water-dropping aircraft.