LOS ANGELES - California Governor Arnold Schwarzenegger has sent National Guard units to help firefighters struggling to contain bushfires raging for 11 days in the northern part of the state.

The move added 200 soldiers to the 18,900 emergency personnel already fighting dozens of fires sparked on June 21 by lightning strikes in the dry, hot wilderness.

In northern California alone, the blazes have devoured 1712 square kilometres, according to the state fire service Calfire, and have begun to close in on Big Sur, a popular hiking and camping location on the Pacific coast some 200 kilometres south of San Francisco.

Some 1,200 buildings are under threat in the Big Sur area, a prime tourist region.

No one has been reported killed by the fires, which have destroyed 29 homes, one business and 21 other buildings and raised concern over air quality.

California is frequently hit by scorching bushfires due to its dry climate, Santa Ana winds and recent housing booms which have seen housing spread rapidly into rural and densely forested areas.

Last October, devastating fires were among the worst in California history, leaving eight people dead, destroying 2000 homes, displacing 640,000 people and causing $US1 billion ($A1.04 billion) in damage.

- AFP