Emergency officials in California are ordering hundreds of people who live along the coast south of San Francisco to leave homes and businesses as a major forest fire continues to blaze just inland. 

What's known as the Basin fire has resisted the efforts of firefighters for a week and has charred more than 120 square kilometres of forest in the famed Big Sur tourist area.

Officials said the flames jumped a fire line cleared through the bush Wednesday morning and headed towards the coastal highway.

People along a smaller section of the road were ordered out Tuesday and dozens of local residents of another part of the coast who were told to leave last week have yet to be allowed to return, Monterey County emergency services spokesman Darby Marshall said.

The mandatory evacuation order applies to 455 people, and 240 other residents are being urged to leave voluntarily, Marshall said

The lightning-sparked fire has destroyed 16 homes.

California Gov. Arnold Schwarzenegger toured the area Wednesday with the head of the Federal Emergency Management Agency, David Paulison.

Schwarzenegger ordered 200 soldiers from the California National Guard to report for firefighting duty, beginning early next week.

At the moment, nearly 19,000 rescue officials and firefighters are battling dozens of forest fires in the state, most in the north around San Francisco and the inland city of Fresno.

Drought, storms blamed

So far this year, drought conditions, high temperatures and a series of lightning storms have contributed to more than 1000 square kilometres being scorched statewide.

Federal fire managers predict an increase in severe wildfire activity in northern California through October due to unusually hot, dry weather and scant rain.

The U.S. government's National Interagency Fire Center, headquartered in Boise, Idaho, released a report on Tuesday predicting significant fire activity to increase or persist in California, Nevada, eastern Montana, Texas and West Virginia.

The agency also increased its national preparedness level Tuesday to Level 5, its highest — a warning that there could be major fires still to come that have the potential to exhaust firefighting resources.

With files from the Associated Press