A military exercise is being blamed for a large grass fire that burned near the St Charles Rifle Range Friday afternoon.

Headingley Fire Chief Doug Hansen said a flare exercise by members of 17 Wing caused the fire that wound up being propelled by the wind over an area of about two or three kilometres.

Fire crews from Headingley, Rosser and Macdonald battled the blaze and managed to bring it under control.

He said hot spots remained Saturday and crews were watching the area which was surrounded by a fire guard.