Wind-whipped flames have chased thousands of residents from some of Los Angeles' wealthiest neighborhoods and threatened the famed Getty Center museum.
It is the latest outbreak in a wildfire season that has triggered mass evacuations and power outages across California.
The fire erupted in the vicinity of the Getty Center at around 1.30am (8.30am Irish time) and by daybreak had swept across more than 200 hectares in the scrub-covered hills around Interstate 405, near some of the city's most expensive homes.
Basketball great LeBron James, "Terminator" star and former California Governor Arnold Schwarzenegger, "Agents of SHIELD" actor Clark Gregg and "Sons of Anarchy" creator Kurt Sutter all said on Twitter they had been forced to flee their homes.
Commuters posted videos on social media of entire slopes engulfed in orange flames close to the highway's edge.
At least five homes had burned down, but no injuries were reported, Mayor Eric Garcetti said at a news conference along with fire officials, warning that he expected property losses to rise.
"This is a fire that quickly spread," he said, urging residents in the mandatory evacuation zone, which encompasses more than 10,000 homes and businesses, to get out quickly.
Basketballer James, an area resident who plays for the Los Angeles Lakers, said he had heeded the warning and had been driving around before dawn with his family looking for shelter.
"Finally found a place to accommodate us!" he wrote a short time later on Twitter. "Crazy night man!"
Kathleen Crandell, a 33-year-old resident of the Pacific Palisades neighborhood adjacent to sprawling parkland in LA's coastal foothills, said she managed to grab her two cats and a handful of other belongings as she fled in her first-ever evacuation.
"This little thing is like a bad dream," Ms Crandell said in an interview with local radio station KPCC.
The fire was stoked by sustained winds of 50 to 65 kilometres per hour, gusting to 80kph, weather officials said.
Officials at the Getty art museum said the fire was burning north of the building, which was designed with thick stone walls to protect its treasures from flames.
Fierce winds fanning wildfires elsewhere across the state in recent days, including a large blaze consuming parts of Sonoma County's picturesque wine country north of San Francisco, were expected to abate later today.
But forecasters with the National Weather Service said high winds would return later in the week and could become the strongest so far this year in southern California.
Sonoma County has been hardest hit in the latest spate of more than a dozen California wildfires, with more than 260 sq km burned and 190,000 people evacuated in a blaze dubbed the Kincade Fire.
Only about 5% of that fire was contained early today after crews lost ground against a wind-driven flare up a day earlier.
More than 4,000 firefighting personnel were battling the Kincade, which has destroyed 96 structures, about a quarter of the homes and other buildings known to have been lost in California wildfires since last week, prompting Governor Gavin Newsom to declare a statewide emergency.
The cause of the Kincade remained under investigation, although Pacific Gas and Electric Co has acknowledged the blaze ignited near a damaged high-voltage transmission tower at about the time a malfunction of the line occurred.
More than 1 million homes and businesses were without electricity this morning, most of those from planned, precautionary power outages.
Forecasts of high winds prompted PG&E to shut off power to 940,000 customers in 43 counties on Saturday night to guard against the risk of touching off wildfires.
PG&E said it expects to issue a weather all-clear for safety inspections and restoration work to begin for the northern Sierras and North Coast, the company said.
The governor has been sharply critical of PG&E, saying corporate greed and mismanagement kept it from upgrading its infrastructure while wildfire hazards have steadily worsened over the past decade.
PG&E filed for bankruptcy in January, citing billions of dollars in civil liabilities from deadly wildfires sparked by its equipment in 2017 and 2018.
After a brief trading halt tripped by its rapid fall, PG&E's stock was down more than 20% on Monday.