An Airforce Spokesperson said that the helicopter which crashed was a Y-12 light aircraft which had taken off from the Weerawila airforce base, in the south.
The aircraft was on a routine observation mission when it crashed in the center of the hilly district.
The two military pilots and two military observers were killed in the crash.
Eye witnesses said that a civilian had sustained injuries due to the crash and had been rushed to a nearby state hospital.
A team has been appointed to inquire into the crash and a separate police investigation is underway.