At least 17 people have died in California as ferocious wildfires continue to sweep across the US state's wine region.

Thousands have been made homeless and more than 200 reported missing, with a state of emergency declared in multiple counties.

The National Guard has been running fuel to fire trucks as so many petrol stations have lost power.

US President Donald Trump has approved a major disaster declaration to send money to the region, promising: "We will be there for you in this time of terrible tragedy and need."

Major fires

Eight counties are affected by 16 major fires, which started on Sunday and have burned through more than 115,000 acres and destroyed at least 2,000 homes.

Firefighters are taking advantage of cooler temperatures and decreased winds to make headway with tackling the blazes.

FalFire operations chief Steve Crawford said on Tuesday: "We need to jump on it and take advantage of this lull before any other wind jumps up.

"There's a lot of devastation out there, people running around who just lost everything."

Sonoma County

There were nine deaths in Sonoma County, three in Mendocino County two in Napa County and one in Yuba County.

Among the dead were 100-year-old Charles Rippey and his wife, 98-year-old Sara Rippey.

The couple's granddaughter told KTVU they had recently celebrated 75 years of marriage, and that they were unable to get out before fires ravaged their home.

Some schools are also keeping children indoors while air quality agencies call on people to limit outdoor activity.