LOS ANGELES (Reuters) - Fires whipped up by hot hurricane force gusts ringed Los Angeles on Saturday, charring thousands of acres and hundreds of homes in California’s largest city and threatening the city’s power supply.

More than 10,000 residents were under mandatory evacuation orders as a fire that exploded overnight in the foothills of the Angeles National Forest barreled into the San Fernando Valley and burned more than 6,500 acres.

The dry Santa Ana winds sweeping in from the desert fanned the fire in the foothills near Sylmar that Los Angeles Mayor Antonio Villaraigosa said had destroyed more homes than any other in the past decade.

Villaraigosa urged residents near Sylmar to leave quickly if they were in harm’s way. “If you wait until the fire gets there you have waited too long ... This fire can be on you in a moment’s notice.”

“We’re at the mercy of the wind. Mother Nature’s not been too good to us for the last 15 hours,” he said later.

The fire raged on both sides of Interstate 5, the main freeway connecting Los Angeles with the north, and the path of transmission lines bringing power to the city of 10 million.

Two of the five main transmission lines had to be taken down because of damage to a converting station, and a third power line was directly damaged by heat, causing 115,000 customers to be without power for 45 minutes.

A separate fire flared south of Los Angeles in Orange County on Saturday morning, charring more than 800 acres and destroying at least 10 structures in the communities of Yorba Linda and Corona, south of Los Angeles.

And, further up the coast near Santa Barbara, firefighters continued to battle the two-day-old blaze in the celebrity enclave of Montecito, where 111 homes have been destroyed. About 40 percent had been contained, a spokesman said.

Northwest of Los Angeles, police closed down Interstate 5 and other roads as 600 firefighters mobilized to fight the Sylmar fire. About 10 percent of the fire has been contained, Los Angeles County Fire Department spokesman Ron Haralson said Saturday afternoon.

Mountains were engulfed in flames and billows of smoke were visible from space by weather satellite. Steady gale-force winds, blowing at 35 mph, periodically gusted up to 75 mph and spread the fire. A map of the fire is at tinyurl.com/sayrefire.

About 300 people, many of them residents of the Oakridge Mobile Home Park where homes burned to the ground, gathered in the Sylmar High School, where the American Red Cross had set up relief services.

“You could see absolutely nothing,” said Jackie Burns, 77, who, along with her husband, Len, fled their mobile home at 3 a.m. as the fire raged through the neighborhood. “It was like looking into a black hole. It looked like the end of the world to me.”

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Some evacuees sobbed as Los Angeles Fire Department Captain Steve Ruda told them the fire had burned down most of the 600 pre-fabricated homes in the mobile park.

“It was an absolute firestorm,” he said. “Firefighters were braving 50-foot flame lengths as they swept across the mobile homes.” Heat from the flames also melted firefighters’ hoses to the pavement, he said.

An additional 24 homes and 10 commercial structures have been damaged or destroyed, Haralson said.

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DRY CONDITIONS ‘PERFECT FOR MORE’

California’s fire season, which traditionally starts in June, has been lengthening and getting worse as the dry state adds homes in fringe areas prone to flames.

Los Angeles, which is home to nearly 10 million people, has been largely spared damage this year. In October of last year 30 blazes raged across Southern California, forcing evacuation of more than 500,000 people and damaging some 2,000 homes.

Marie Larsen, 70, another evacuee who took refuge at the Sylmar school, said she grabbed her suitcase -- still packed from a month ago when she fled her home during the Sesnon fire -- and left after six police officers banged on her door.

The Los Angeles area remains on alert for more fires, said Daniel Berlant, a spokesman at the California Department of Forestry and Fire Protection.

“It’s the dry conditions that make it perfect for more fires,” he said.