The Hollywood Hills are blazing uncontrollably as the worst wildfires in the history of Los Angeles raged across the city, killing  at least five people, destroying hundreds of homes and stretching firefighting resources and water supplies to the limit.

A crescent of flame squeezed Los Angeles in a huge pincer visible from space. More than 100,000 people were ordered to evacuate as dry, hurricane-force winds hindered firefighting operations and spread the flames.

"This firestorm is the big one," Los Angeles Mayor Karen Bass told a press conference after rushing back to Los Angeles upon cutting short an official trip to Ghana.

At least six separate wildfires were burning in Los Angeles County. Three of them were totally out of control, including a pair of huge conflagrations on the city's eastern and western flanks and the smaller Sunset Fire raging in Hollywood Hills just above Hollywood Boulevard and its Walk of Fame.

Satellite images show entire neighbourhoods burning. – Reuters/Maxar Technologies

All but one of them were 0 per cent contained according to state officials, including a pair of major conflagrations on the eastern and western flanks of the city that continued to grow as night fell.

In between, the so-called Sunset Fire in Hollywood Hills scorched 50 acres (20 hectares), Cal Fire said. Helicopter crews doused the flames with water drops, appearing to impede its rapid advance.

The LA Fire Department issued an evacuation order for people in an area within Hollywood Boulevard to the south, Mulholland Drive to the north, the 101 Freeway to the east and Laurel Canyon Boulevard to the west – all iconic addresses.

Though relatively small compared to the others, the Sunset Fire burned just above Hollywood Boulevard and its Walk of Fame. It would need to cross the 101 Freeway to endanger the Hollywood sign and Griffith Observatory further up in the hills.

LA fire chief says at least 2 people killed and over 1000 structures destroyed in fires. – AP

On the west side of Los Angeles, the Palisades Fire consumed 15,832 acres (6406 hectares) and hundreds of structures in the hills between Santa Monica and Malibu, racing down Topanga Canyon until reaching the Pacific Ocean on Tuesday. It was already one of the most destructive fires in Los Angeles history.

Aerial video showed block after block of smouldering homes in Pacific Palisades, the smoky grid occasionally punctuated by the orange blaze of another home still on fire.

To the east, in the foothills of the San Gabriel Mountains, the Eaton Fire claimed another 10,600 acres (4289ha) and killed at least five people, Los Angeles County Sheriff Robert Luna said.

Three people had been arrested for looting, law enforcement officials said.

Private forecaster AccuWeather estimated initial damage and economic loss at more than $50 billion.

"We're facing a historic natural disaster. And I think that can't be stated strong enough," Kevin McGowan, director of emergency management for Los Angeles County, said.

Even though forecasters said winds would subside on Wednesday night, so-called red flag conditions were expected to remain until Friday.

Nearly 1 million homes and businesses lost power in Los Angeles County, according to PowerOutage.us.

"The wind whipped up, the flames were up about 30 or 40 feet (9 to 12 meters) high, and you hear 'pop, pop, pop'. It sounded like a warzone," Kevin Williams, an Eaton Fire evacuee, said at an evacuation centre in Pasadena, describing gas canisters at his neighbors' homes that began exploding under the heat of the flames.

Palisades Fire causes devastation along iconic California highway. – Reuters

The scale and spread of the blazes stretched already exhausted firefighting resources.

"There are not enough firefighters in L.A. County to address four separate fires of this magnitude," said Los Angeles County Fire Chief Anthony Marrone.

Firefighters from six other states were being rushed to California, while an additional 250 engine companies with 1000 personnel were being moved from Northern California to Southern California, Marrone said.

Water shortages caused some hydrants to run dry in upscale Pacific Palisades, officials said.

"We pushed the system to the extreme. We're fighting a wildfire with urban water systems, and that is really challenging," Janisse Quinones, chief executive of the Los Angeles Department of Water and Power, said.

Eaton Fire scorch Los Angeles area hills, homes. – AP

Pacific Palisades relies on three tanks that hold about a million gallons (3.78 million litres) each, and the demand for water to fight fires at lower elevations was making it difficult to refill water tanks at higher elevations, she said.

Some hydrants ran dry at around 3am, but by Wednesday afternoon, all three of those tanks and all 114 reservoirs throughout the city were refilled, Quinones said.

Nestled in the hills with spectacular ocean views, Pacific Palisades is one of the most expensive neighbourhoods in the country with a typical home valued at $3.7 million as of the end of 2023, according to Zillow, more than all but four other zip codes in the United States.

The fires struck at an especially vulnerable time for Southern California, which has yet to see significant rainfall since the start of the water year in October.

Then came the powerful Santa Ana winds, bringing dry desert air from the east toward the coastal mountains, fanning the flames of the wildfires while blowing over the hilltops and down through the canyons.

President Joe Biden, who stayed put in Los Angeles after Air Force One was grounded due to high winds on Tuesday, joined California Governor Gavin Newsom at a Santa Monica fire station to get a briefing firefighting efforts.

In his final days as president before handing off to President-elect Donald Trump on January 20, Biden cancelled an upcoming trip to Italy in order to focus on directing the federal response to the fires, the White House said.

"The impacts of (the fires include) over one thousand structures already destroyed, a hundred-plus thousand people that have been evacuated, lives lost, traditions, lifestyles, places torn asunder," said Newsom, who declared a state of emergency.

Biden pledged any help he could provide in his final days in office before handing off to President-elect Donald Trump on January 20.

"We're doing anything and everything and as long as it takes to contain these fires ... to make sure you get back to normal," Biden said. "It's going to take time."

Biden briefed on LA wildfires, vows federal gov't will 'do anything and everything' to help. – AP

Trump called the deadly wildfires “a true tragedy” and criticised Newsom for what he said were policies that led to a lack of water to fight the fires.

"This is a true tragedy and it was a mistake of the governor, and you could say the administration. They don't have any water. They didn't have water in the fire hydrants," he said.

Speaking alongside Republican leaders at the US Capitol, Trump blamed the state’s conservation policies for the lack of available water.

"They sent (the water) out to the Pacific because they're trying to protect a tiny little fish, which is in other areas, by the way," Trump said.

"They have plenty of water. They don't have a drought. They send it out to the Pacific and it's crazy." 

"So what's happening in California is a true tragedy. I know those areas very well. I have many friends living in those houses." 

Trump calls California wildfires a 'true tragedy', criticises Governor Newsom. – Reuters