An Arizona forestry official says 19 firefighters have died battling a fast-moving wildfire.

Forestry spokesman Art Morrison says the firefighters were caught by the fire yesterday afternoon. He says they were forced to deploy their fire shelters.

The wildfire also prompted evacuations of at least 50 homes.

About 200 firefighters are fighting the wildfire.

It is the country's deadliest wildfire involving firefighters for at least 30 years.

The specially trained "hotshot" firefighters were forced to deploy their fire shelters - tent-like structures meant to shield them from flames and heat - when they were caught near an Arizona town, Mr Morrison said.

"The entire hot shot crew had been killed by the fire," Prescott Fire Chief Dan Fraijo said.

The fire started on Friday and spread to 2,000 acres yesterday amid high temperatures, low humidity and windy conditions.

The National Fire Protection Association previously listed the deadliest wildland fire involving firefighters as the 1994 Storm King Fire in Colorado. It killed 14 firefighters who were overtaken by a sudden explosion of flames.

Officials later said that the blaze had destroyed an estimated 200 homes.

Dry grass near the communities of Yarnell and Glen Isla fed the fast-moving flames, which were whipped up by wind and raced through the homes.

The Red Cross has opened two shelters in the area - at Yavapai College in Prescott and at the Wickenburg High School gym.