US President Donald Trump has said that “gross mismanagement of forests” is to blame for two unchecked wildfires burning in California, where nine people have been killed and hundreds of thousands forced to evacuate.

“There is no reason for these massive, deadly and costly forest fires in California except that forest management is so poor,” he wrote in a Twitter post early on Saturday.

“Billions of dollars are given each year, with so many lives lost, all because of gross mismanagement of the forests. Remedy now, or no more Fed payments!,” he added.

His reposne to the fires drew criticism across social media and celebrities like popstar kathy Perry, who described his tweet as an “absolutely heartless response”.

She added: “There aren’t even politics involved. Just good American families losing their homes as you tweet, evacuating into shelters.”

Others questioned if he knew the difference between wildfires and forest fires. They also attacked him for issuing a tweet which was all about money, with no sympathy or thought for those whose lives were affected by the tragedy.

As people perished in the fires, hundreds of thousands ordered to evacuate across California, with one rapidly spreading blaze threatening the resort of Malibu, home to Hollywood stars.

The fatalities were reported in a massive late-season inferno in the town of Paradise, in Butte County north of the state capital Sacramento, where some 6,700 structures went up in flames - officially becoming California’s most destructive fire on record.

The fast-moving blaze, which authorities have named the “Camp Fire”, broke out Thursday morning. Fanned by strong winds, it has scorched 36,400 hectares and is only five percent contained, the California Fire Department (Cal Fire) said late Friday.

Other large fires raged in southern California, including one just north of Los Angeles and another in Ventura County near Thousand Oaks, where a Marine Corps veteran shot dead 12 people in a country music bar on Wednesday night.

“The magnitude of destruction we have seen is really unbelievable and heartbreaking and our hearts go to everybody who has been affected by this,” said Mark Ghilarducci, the director of the California Governor’s Office of Emergency Services.

Governor-elect Gavin Newsom declared a state of emergency to provide assistance to the fire-hit areas.

Late Friday Butte County Sheriff Korey Honea said it was his “sad duty” to update the Camp Fire death toll to nine.

“I don’t have all of the details because we have investigators out on the field” trying to reach the locations where casualties were reported, Honea told a press conference.

But he did say that four people were found inside a vehicle in the Paradise area, while another was found nearby outside the vehicle. Three more were found outside a residence, and one inside a house.

Dozens of other people were reported missing.

Residents who escaped Paradise posted harrowing videos to social media as they drove through tunnels of swirling smoke and orange flames to outrun the wildfire.

The flames destroyed hundreds of homes, a hospital, a gas station, several restaurants and numerous vehicles, officials said.

Mandatory evacuation orders were issued for more than 52,000 people in the scenic area in the foothills of the Sierra Nevada mountains.

“The whole lower side of Paradise is totally engulfed in flames right now,” Kevin Winstead, a resident of nearby Magalia, told KIEM TV. “All of it is engulfed in flames right now.

“Not one home will be left standing,” he said. “I’m devastated.” “We’re just hoping that our brand new home that we were hoping to move into tomorrow is not burned to the ground,” Winstead said.

The residents of the beachside enclave of Malibu and the gated community of Hidden Hills, where celebrities including Kim Kardashian and Grammy Award winners Drake and The Weeknd live, were ordered to leave by authorities.

Australian businessman Jon Sully, his wife Kath and their three children Spencer, Isabelle and Hamish, also had to make a mad dash from their Hidden Hills home as the fire line approached on Thursday night.

“We got the first mandatory at 7.06pm last night and packed the kids, dogs, passports, photos etc in the car,” Mr Sully, a co-founder of retail leasing platform StoreMatch, told AAP.

“We could see the red glow over the ridge that was flaring up so didn’t hesitate to go.”

They went to a friend’s house in nearby Agoura Hills but three hours later were forced to evacuate again when police on loudspeakers drove around the neighbourhood warning they were in peril.

They made it to a third friend’s house and spent a nervous night. The threat remains for the region.

“The smoke was apocalyptic,” Mr Sully said.

In southern California, authorities said some 200,000 people are under evacuation orders.

The Ventura County Fire Department said the “Woolsey Fire” had burned around 35,000 acres, was not contained, and that evacuation orders were issued for some 88,000 homes in the county and neighboring Los Angeles County.

“It is critical that residents pay close attention to evacuation orders,” the Los Angeles County Fire Department said on Twitter. “This is a very dangerous wind-driven fire.” The “Woolsey Fire” has jumped Highway 101 near the town of Agoura Hills and portions of the main coastal north-south artery have been shut down, triggering mandatory evacuations, including the entire city of Malibu.

The flames destroyed Paramount Ranch, a movie set for cowboy shows including HBO’S Westworld, officials said.

Cal Fire posted footage taken from helicopters that showed flames racing over hill ridges towards multi-million dollar mansions.

“We heard this was coming so we set up on the sprinklers and we hosed the whole house down,” said Patrick Henry, a Malibu resident. “We pretty much had enough time to get the dogs in the trunk.” Malibu is one of the most in-demand locations in California for Hollywood stars seeking privacy and luxury, and has been home to Leonardo DiCaprio, Jack Nicholson, Jennifer Aniston, Halle Berry, Charlize Theron, Brad Pitt and a host of other celebrities.

Reality TV star Kim Kardashian West, who lives just north of coastal Malibu in Calabasas, revealed on Instagram that she was forced to flee her home.

“Just landed back home and had 1 hour to pack up & evacuate our home. I pray everyone is safe,” she said.

TV star Charlie Sheen tweeted that his father, Martin Sheen, and his mother Janet were both missing - but the pair surfaced unharmed hours later at a beachside evacuation spot.

“We’re fine, we’re at Zuma Beach and we’re probably going to sleep in the car tonight,” Martin Sheen told Fox News 11, addressing his adult children.

Sheen said this was the worst fire he had seen in 48 years of living in Malibu. Director Guillermo del Toro tweeted that Bleak House, his museum of horror movie memorabilia, was also in the path of the flames.

The fire zone is a popular area for Australian expatriates to live. More than 3000 hectares of land and at least 20 homes have been destroyed as two fires, powered by strong winds, were unstoppable as they headed west, jumped the 101 Freeway and roared towards Malibu on the coast.

Authorities said about 75,000 homes in Ventura and Los Angeles counties are under mandatory or voluntary evacuation orders and the number could grow.