Hundreds of homes are feared lost in fast-moving wildfires in the US state of Colorado, with flames tearing through areas dried out by a historic drought.
At least 1,600 acres have burned in Boulder County, much of it suburban, with warnings that deaths and injuries were likely as the blaze took hold of hotels and shopping centres in the town of Superior.
"We know that approximately 370 homes in the Sagamore subdivision ... have been lost. There's a potential of 210 homes lost in Old Town Superior," Boulder County Sheriff Joe Pelle told a news conference.
"The Target shopping complex in Superior is on fire; the Element Hotel in Superior is fully engulfed.
"I'd like to emphasise that due to the magnitude and intensity of this fire and its presence in such a heavily populated area, we would not be surprised if there are injuries or fatalities."
The Colorado Sun newspaper reported that a number of people had been treated for burns, with at least six patients at one hospital.
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Footage broadcast by CBS showed what appeared to be an apartment complex on fire, as firefighters attempted to dowse the flames.
One video on Twitter showed a fire in a car park, with trees and grass ablaze, as strong wind pushed smoke around.
Thousands of people have been told to flee the fast-moving fire, which is thought to have begun when power lines were toppled by gusting winds.
The 20,000-strong town of Louisville, along with the 13,000 residents of Superior, have been told to get out, with the National Weather Service describing the situation as "life-threatening".
Wind gusts of over 160km/h have been reported in some places, fanning the flames and complicating firefighting efforts by preventing aircraft from taking to the skies.
Colorado Governor Jared Polis declared a state of emergency, over what he said was a devastating fire.
Unlike previous blazes in the state, he said, this one is not in the countryside; it is where people live.
"This area is right in and around suburban sub-developments, stores," he said.
"It's like the neighbourhood that you live in. It's like the neighbourhood that any of us live in. And so 1,600 acres near a population centre can be and is, in this case, absolutely devastating."
Like much of the American West, Colorado is in the grip of a years-long drought that has left the area parched and vulnerable to wildfire.
Although fires are a natural part of the climate cycle, and help to clear dead brush and reduce disease in vegetation, their scale and intensity is increasing.
Scientists say a warming climate, chiefly caused by human activities like the unchecked burning of fossil fuels, is altering weather patterns.
This prolongs droughts in some areas and provokes unseasonably large storms in other places, phenomena that are expected to get worse as worldwide average temperatures continue to climb.
Daniel Swain, a meteorologist at the University of California, tweeted that it was "hard to believe" these fires were taking hold in December, usually a quieter time for blazes.