Los Angeles  - A raging California wildfire doubled in size Monday and threatened the city of Los Angeles, while two firefighters were killed when their vehicle tumbled down a mountain as they fought the region's worst blaze of the year.

As they struggled to deal with the death of their comrades, firefighters also had to deal with the dangers of residents who refused to leave their homes despite the evacuation orders to over 6,000 homes. Five such residents on a ranch near Gold Creek remained stranded late Monday after they appealed for rescue, as heavy smoke and strong winds made it impossible for a helicopter to reach them.

The Station Fire has already destroyed at least 53 homes and threatens some 12,000 more. The fire could also knock out the transmitter towers for much of the television, radio and cellphones in the Los Angeles area.

"The fire is headed just about anywhere it wants to," LA County Fire Deputy Chief Mike Dietrich said. "This is a very angry fire. Until we get a change in the weather conditions, I am not overly optimistic."

The flames in the Los Angeles National Forest sent a huge plume of smoke into the air over the city and could be seen for miles, while authorities warned of poor air quality.

Further to the south, the Oak Glen Fire threatened 2,000 homes in San Bernardino County as dry and hot conditions across the region fanned flames that raced through tinder-dry brush.

Some 50 helicopters and more than 6,400 firefighters have been mobilized to battle the blazes, which have now burnt over 34,000 hectares since they ignited last week.

California Governor Arnold Schwarzenegger visited the base of operations battling the blaze and noted the difficult conditions hindering firefighting, including temperatures near 35 degrees Celsius and dry brush that had not burned for years. On Friday, Schwarzenegger had declared a state of emergency to speed relief efforts.

"Fires are burning from the north - the northern border of California - all the way south, and from the Pacific Ocean to the Sierra Nevada (mountain range)," said Schwarzenegger. "We have fires everywhere. We have eight large fires around the state of California right now. But the firefighters have fanned out across California and they're doing an amazing job."

Elsewhere in the state, a fire destroyed 11 homes north-east of Sacramento and 100 homes were threatened, while one home had been destroyed in a 2,500-hectare blaze near Pinnacles National Monument in Monterey County. A further 50 homes were threatened by a 1,700- hectare blaze in Yosemite National Park that was 50 per cent contained. (dpa)