Wildfires have been raging across parts of Colorado, destroying buildings and forcing thousands of people to flee their homes.

A fire in the Pike National Forest, west of Colorado Springs, is reported to have spread over 30,000 acres and has engulfed the city of Denver in smoke and ash. State Governor Bill Owens, who flew over the area, said the scene resembled a "nuclear winter".

Fires at the base of Storm King Mountain, between Vail and Aspen, have destroyed about 40 buildings including 24 homes and led to the evacuation of about 3,000 people from the resort of Glenwood Springs.

There have been no reports of casualties.

Health officials in Denver issued a health warning and advised residents to stay indoors as a yellow haze swept over the city.

"All of Colorado is burning today. It is a very, very serious situation," Mr Owens said on Monday.

Volunteers join in

The National Guard and civilian volunteers have been helping fire crews to try to contain the flames.

It is believed the blaze in the national forest was started by an illegal camp fire on Saturday. Officials said the fire was probably ignited by an underground coal seam that has been burning for years.

The blaze was then fanned by strong winds and was soon consuming hundreds of acres every hour.

Homes in the mountains south-west of Denver have been evacuated and many roads have been closed.

Flames are threatening populated areas

In Glenwood Springs, firefighters were on ridges above the town trying to protect homes.

The situation has brought back memories of wildfires near Storm King Mountain in 1994 in which 14 firefighters were killed.

Mayor Rick Davis said: "We learned from Storm King that dwellings can be rebuilt but you don't want to lose any life."

It was hoped that higher humidity levels, calmer winds and lower temperatures on Monday would ease the situation.

In south-west Colorado, a fire on a mountain ridge north of Durango has burned about 6,500 acres.

Two camp sites were evacuated and several hikers and campers were picked up by helicopter.