US firefighters die battling wildfire

At least 19 firefighters have been killed while battling a wildfire in the US state of Arizona.

An Arizona forestry official said on Sunday that the firefighters died while battling a fast-moving wildfire in Yarnell Hill, Yavapai County.

Forestry spokesman Art Morrison said the firefighters were caught by the blaze on Sunday afternoon and were forced to deploy their fire shelters, tent-like structures meant to shield them from flames and heat, according to the Associated Press news agency.

Morrison added that the firefighters were members of a specially-trained "hotshot" crew, responsible for digging a fire line and creating an escape route.

The fire in Yarnell Hill started on Friday and spread to an area of more than eight square kilometres on Sunday amid high temperatures, low humidity and windy conditions. 

The wildfire also prompted evacuations of at least 50 homes.

Around 200 firefighters are fighting the blaze.

Local news site the Arizona Republic reported the fire was fast-moving and that by Sunday night had not been contained.

Federal help was expected starting on Monday, it reported, but officials expected that least 250 homes, which corresponds to about half of the town of Yarnell Hill, would be destroyed by the inferno.

Yavapai County is located in central Arizona.