The army initially reported that during fighting with Kurdish rebels on May 13 a helicopter had crashed for technical reasons.
But the outlawed Kurdistan Workers' Party, or PKK, later circulated video it said showed the helicopter being downed by one of its fighters.
The weapon used, according to some observers, appears to have been a MANPAD, or shoulder-launched surface-to-air missile, AP reported.
The Turkish army said Thursday "it may have been downed as a result of fire from terrorist elements from a yet unknown type of surface-to-air, possibly an air-defense missile."
Turkish security forces and Kurdish rebels have been locked in conflict since the collapse of a cease-fire last summer.