A state of emergency has been declared in four counties in southern California where wildfires have killed at least 13 people.
Firefighters are struggling to contain the blazes
Raging for almost a week, the blazes have forced tens of thousands to flee and closed several main roads.
"These are the worst fires we've faced in California in 10 years," Governor Gray Davis said.
As high winds fanned the flames, officials said no end was in sight.
The Californian authorities are now battling fires on 10 separate fronts in Los Angeles, San Diego, Ventura and San Bernardino counties.
More than 300,000 acres (120,000 hectares) have been destroyed and at least 800 homes reduced to ashes.
The BBC's Robert Nisbet in San Bernardino county said the flames were travelling up to four kilometres (2.4 miles) an hour and described the scene as "almost apocalyptic".
California Fire Destruction
13 people killed
800 houses destroyed
30,000 homes under threat
300,000 acres consumed
7,000 firefighters deployed
Earlier, highway patrol staff in the county said two people were found dead in their car, apparently trying to escape a fire.
"We were literally running through fire," said Lisza Pontes, 43, who escaped a fire in San Diego county with her family after the roar of the flames woke them up.
'Pack your belongings'
"The fire has now gone into outlying parts of the city of San Diego and has also crossed the border into Mexico," said Adriana
Uribe of the San Diego County Sheriff's Department.
Sheriff William Kolender said parts of the city of 1.2 million
people were being evacuated and told residents "not to hesitate to pack
your belongings and leave" if the fire came their way.
San Bernardino County, about 30 miles (48 kilometres) east of Los Angeles, has also been hit hard - with around 100,000 acres (40,470 hectares) destroyed.
The county's fire department said on Sunday the blaze was only 23% contained and had already caused more than $6m in damage.
Entire towns have been evacuated, including people in juvenile probation camps and airport employees, while sports events have been postponed.
At least 30,000 homes across the region are said to be at risk while there were reports of attempted looting.
San Bernardino coroner said a 70-year-old man had died while leaving his home and a 93-year-old man while watching his burn.
Dozens of the 2,500 firefighters have suffered second degree burns, minor burns and smoke inhalation.
Air quality has been described as "horrific" and regional authorities have issued advisories urging people to limit or discontinue outdoor activities.
Major interstate highways have been closed and power lines are under threat, prompting state power grid operators to urge people to conserve energy.
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