From the ashes of a mobile home and RV park, US President Donald Trump said he came to the heart of California's killer wildfire to fully grasp the scale of the desolation wrought on the landscape.

"We're going to have to work quickly ... Hopefully this is going to be the last of these because this was a really, really bad one," said the President, standing amid the crumpled foundations of homes and twisted steel of melted cars.

"I think everybody's seen the light and I don't think we'll have this again to this extent," Trump said in Paradise, the town largely destroyed by a wildfire that he called "this monster".

With that bold and perhaps unlikely prediction, Trump pledged that improved forest management practices will diminish future risks.

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The declaration evoked his initial tweeted reaction to the fire, the worst in the state's history, in which he seemed to blame local officials and threatened to take away federal funding.

When asked if seeing the historic devastation, which stretched for kilometres and left neighbourhoods destroyed and fields scorched, altered his opinion on climate change, Trump answered: "No".

The President has long voiced scepticism about man's impact on the climate and has been reluctant to assign blame to a warming earth for the increase in the frequency and intensity of natural disasters.

At least 71 people died across Northern California, and authorities are trying to locate more than 1000 people, though not all are believed missing.

More than 5500 fire personnel were battling the blaze that covered 590 sq km and was about 50 per cent contained, officials said.

For Trump, it was a day to comfort a state grieving from twin tragedies, wildfires in both Northern and Southern California as well as a mass shooting at a popular college bar north of Los Angeles.

Wearing a camouflage "USA" hat, Trump gazed solemnly at the devastation in Paradise.

President Donald Trump talks with from left, Governor-elect Gavin Newsom, FEMA Administrator Brock Long, Jody Jones, Mayor of Paradise, and California Governor Jerry Brown.
President Donald Trump talks with from left, Governor-elect Gavin Newsom, FEMA Administrator Brock Long, Jody Jones, Mayor of Paradise, and California Governor Jerry Brown.

Several burned-out buses and cars were nearby. Trees were burned, their branches bare and twisted. Homes were totally gone; some foundations remained, as did a chimney and, in front of one house, a Mickey Mouse lawn ornament.

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"It's going to work out well, but right now we want to take care of the people that are so badly hurt," Trump said visiting what remained of the Skyway Villa Mobile Home and RV Park.

He noted "there are areas you can't even get to them yet" and the sheer number of people unaccounted for.

"I think people have to see this really to understand it," Trump said.

The president later toured operation centres, met response commanders and praised the work of firefighters, law enforcement and representatives of the Federal Emergency Management Agency.

Trump took a helicopter tour en route to Chico before he toured Paradise.

- AP