Los Angeles, Dec 7 (IANS): Wildfires that have already devoured a large swath of territory continue to rage in the hills north of Los Angeles, threatening America's second largest city.

With several multimillion-dollar mansions in the Bel-Air neighbourhood already ablaze and flames threatening the Getty Centre arts complex and its priceless collection, officials on Wednesday closed down part of Interstate 405, a key north-south artery, reports NBC News.

"These are days that break your heart. But these are also days that show the resilience of our city," Los Angeles Mayor Eric Garcetti said.

California Governor Jerry Brown, who had earlier declared a state of emergency in Ventura, was monitoring the Los Angeles fire while hundreds of homeowners in Bel-Air and the nearby Sherman Oaks neighbourhood joined the tens of thousands of other Southern California residents who have fled the infernos that have scorched more than 83,000 acres and reduced scores of homes and businesses to ashes.

The massive blazes showed no signs of stopping as roaring winds fuelled flames that feasted on the tinder-dry conditions in the region.

By Wednesday evening, it had already consumed half a dozen mansions and 150 acres of some of the city's most expensive properties, The Los Angeles Times reported.

The Los Angeles Fire Department said only 5 per cent of the fire had been contained.

By Thursday, wind gusts should increase to around 30 to 50 mph along with low humidity, "which means very, very dry conditions, very windy conditions which is a recipe for explosive fire growth", said Rich Thompson, a meteorologist with the National Weather Service.

More than 1,770 firefighters and police officers are fighting the wildfires.

No fatalities or civilian injuries were reported, but 150 structures have been destroyed and 12,000 more continue to be under threat, fire officials said.