A raging wildfire in southern California has triggered a mandatory evacuation order for much of the beachside city of Malibu.

The fire broke out on Thursday north west of Los Angeles and roared south, jumping the US 101 freeway early on Friday and sweeping into the Santa Monica Mountains.

Malibu, known as the home of many Hollywood stars, has about 13,000 residents and lies along 21 miles of coast at the southern foot of the mountain range.

Los Angeles County Fire Department tweeted that the fire is heading towards the ocean, punctuating the message with the declaration: “Imminent threat!”

Malibu officials initially said the order applied to the entire city but have now defined an area that is approximately the western two-thirds of the community.

The director of the California Governor’s Office of Emergency Services says another fire in northern California has claimed lives.

Mark Ghilarducci said the number of deaths was not known. He said there are also injuries.

A fire official said the blaze in northern California nearly quadrupled in size overnight.

Captain Scott McLean of the California Department of Forestry and Fire Protection said the fire near the town of Paradise has grown to nearly 110 square miles.

The blaze has devastated the town of 27,000 people and is moving north into Sierra Nevada foothill communities.

Butte County Sheriff’s Office said an evacuation ordered had been issued for the small communities of Stirling City and Inskip.

Cal Fire Captain Bill Murphy said winds have calmed down in the valley but there are “shifting, erratic winds” with speeds of up to 45mph along ridge tops.

The blaze also reached the edge of Chico, a city of 90,000 people.

Mr Murphy said firefighters were able to stop the fire at the edge of the city, where evacuation orders remain in place.

Smoke from wildfires obscures the San Francisco skyline
Smoke from wildfires obscures the San Francisco skyline (Eric Risberg/AP)

Authorities issued an unhealthy air quality alert for parts of the San Francisco Bay Area as smoke from the wildfire drifted south.

The air in San Francisco was hazy and the smell of smoke overwhelming, prompting officials to declare air quality unhealthy.

They advised older people and children to move physical activities indoors. All people were encouraged to limit their outdoor activities.