The crash happened near a hospital in the city of Flagstaff in Arizona.

All three people on one of the helicopters died - including a patient and the pilot.

It is not clear how many of the others who died were in the second helicopter or on the ground.

Both of the helicopters were heading for the same Flagstaff hospital when the collision occured.

The helicopters crashed in a wooded area about half a kilometer from the Flagstaff Medical Center, spreading debris across a wide areas and triggering a brush fire.

"They're not recognisable as helicopters," Captain Mark Johnson, a spokesman for the Flagstaff Fire Department, said.

The cause of the collision is being investigated.

Agencies