(Updates with fire spread to 600 acres, 300 people evacuated, cigarette possible cause of fire)

By Mary Milliken

LOS ANGELES, May 8 (Reuters) - Firefighters evacuated 300 residents of an affluent Los Angeles neighborhood and pushed back flames from the edge of upscale homes as a wildfire in the city's largest park flared on Tuesday night.

The blaze in Griffith Park, which authorities say might have been started by a careless cigarette smoker, began in the early afternoon and was fanned by unseasonably high temperatures and hot Santa Ana winds through the brittle, rain-thirsty brush.

Firefighters evacuated people from the hilly park just east of the landmark Hollywood sign, from a museum and from the city's zoo early in the afternoon.

Some 600 acres (250 hectares) had burned by 11 p.m., Los Angeles Mayor Antonio Villaraigosa said.

The orange flames above the Los Feliz neighborhood, just miles from Hollywood, were visible across much of the sprawling city. The flames resurged after nightfall, when 25 percent of the fire was reported to be contained.

"About 300 people have been evacuated up to now, but unfortunately around 25 people have refused to leave their homes," Villaraigosa said in a news conference from the perimeter of the park.

Police Chief William Bratton said the fire may have been accidental, caused by "the careless disposal of a cigarette."

Arson investigators were questioning a man who was seen walking out of the brush near the fire with burns on his body. He was hospitalized, but has not been charged with starting the fire, Fire Chief Doug Barry said.

No other injuries were reported.

FIREFIGHTERS IN HOMES

For the night, Barry said, the "fire had laid down" and firefighters had stopped the flames from advancing toward the homes. Hundreds of firefighters on the ground and five water-dropping helicopters would work throughout the night and fresh crews would be deployed in the morning.

City Councilman Tom LaBonge said, "there are firefighters with hoses through the front doors of homes, going out the balconies and fighting the fire right up to the edge of the brush."

L.A. media and residents were calling it Griffith Park's worst fire in decades, maybe since the 1930s.

The park, with its Greek Theatre, Observatory, zoo, trails and panoramic views, is a haven for hikers and families in the heart of the second largest U.S. city. The fire destroyed one of the favorite perches of hikers known as Dante's View.

Zoo spokesman Jason Jacobs said many zoo employees were sent home but that the approximately 1,000 animals stayed behind, along with animal care staff and veterinarians.

"The animal care staff is keeping an eye on the fire and on reports from the fire department and will take action if need be," he said.

Tuesday's fire was the second in as many months in the area as Southern California registers some of the driest conditions in 80 years.

Two Illinois teenagers were accused of starting a 150-acre (60-hectare) brush fire in an area near the Hollywood sign in March.

Fire officials have issued a "red flag" warning for much of Southern California, denoting extremely high fire danger.

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