The photos show the barefoot men dressed in orange jumpsuits kneeling in a street as a crowd of people, many of them apparently militants, look on.
Black-clad men wearing balaclavas are then pictured shooting them with pistols.
The photos were said to have been taken in Anbar, where security forces are battling to regain ground from the militants, especially around provincial capital Ramadi, which the militants seized in May.
But no precise location was given, and the authenticity of the images could not be independently confirmed.
The jihadist group often documents the killings, which have included burnings, beheadings and drownings, in photos and videos released by its propaganda arm in a bid to inspire fear and draw new recruits.