The Islamic State (IS) group on Monday released pictures of the execution of 13 men described as anti-jihadist Sunni tribal fighters near the northern city of Tikrit.
Three pictures published on a jihadist forum and pro-IS social media accounts show the execution of the men wearing orange jumpsuits.
Local residents confirmed that a mass execution had taken place on a large roundabout six kilometres (four miles) east of the city of Tikrit at around 3:30 pm (1230 GMT).
The first picture shows 11 men kneeling, heads bowed, with one black-clad and masked gunman behind each one and black IS flags in the background.
The next picture shows the gunmen brandishing their handguns after the execution and in the third a small gathering of onlookers, including children, can be seen near 13 bodies, which have been dragged off the roundabout`s central island and onto the road.
Residents said the roundabout is at an intersection for roads leading to Tikrit, Kirkuk and the town of Al-Alam.
They said the men who were executed were members of an anti-IS group of Sunni tribal fighters known as the Knights of Al-Alam who were captured by jihadists in Tikrit and Al-Alam around 10 days earlier.
The city of Tikrit has been under IS control since the beginning of the jihadists` major offensive in Iraq six months ago.
Iraqi government forces, backed by Shiite militia and in some areas by Sunni tribal fighters have inflicted a string of defeats on the jihadists in recent weeks.