The attackers fired at the first responders as they were getting out of a helicopter in the Araucania Region, The Santiago Times reported.
Two of the firefighters were transported to local hospitals with injuries.
Forestal Mininco, the Chilean company that employs the firefighters, said some 100 fires were started simultaneously across the Libertad Capesina estate Sunday night.
Much of the land that is now owned and operated by Forestal Mininco is also claimed by the indigenous Mapuche people.
Notable deaths of 2014 [PHOTOS]