Iraqi authorities say a mass grave containing the bodies of 16 men, each shot in the head, has been found northeast of Baghdad in an area once controlled by the Islamic State group.

Mohammed Hassan, the mayor of Khanaqin, says the discovery was made Wednesday afternoon in the nearby village of Koubashi, some 140 kilometers (87 miles) northeast of Baghdad.

Medical officials in Khanaqin hospital, speaking on condition of anonymity because they are not authorized to brief the media, confirm receiving 16 decomposed bodies of men shot in the head.

The Islamic State extremist group captured Koubashi during its rampage across northern and western Iraq last year. Hassan says the killings took place before Iraqi security forces drove the militants out a month ago.