Sunni Muslim militants fighting to set up a hardline Islamic regime in Iraq posted shocking photos over the weekend showing captured Iraqi government soldiers being loaded by the dozen onto trucks, then gunned down in a mass grave on the side of the road.

The graphic images were taken in the Salahuddin province north of Baghdad, after militants with the Islamic State of Iraq and the Levant seized an Iraqi Army base in the area, reported the Long War Journal, a publication which tracks Islamist militant groups.

A photo essay posted on social media platforms associated with the militant group appeared to document the disturbing events as they played out.

(Warning: some of the images are graphic and may be unsettling to some readers.)

The photos documented dozens of men being loaded onto flatbed trucks then taken to a shallow ditch where it appears that they were summarily executed face down with their hands tied behind their backs.

The photos which were authenticated by the Iraqi Army's top spokesman showed Iraqi soldiers loaded onto trucks then driven to their mass execution. ISIL posted this and other photos on social media accounts.

The photos which were authenticated by the Iraqi Army’s top spokesman showed Iraqi soldiers loaded onto trucks then driven to their mass execution. ISIL posted this and other photos on social media accounts.

After the men were dead, the ISIL militants appeared to pose with their guns aimed at the corpses lined up in the ditch and holding black flags.

The men with tied arms were lined up over a shallow ditch and executed (Image source: jihadi social media postings)

The men with tied arms were lined up over a shallow ditch and executed (Image source: jihadi social media postings)

Another image captured earlier showed the men who were about to be executed leaning on each other in a line with a machine gun pointed at them.

Image source: ISIL social media postings.

Image source: ISIL social media postings.

This image posted on a militant website on Saturday, June 14, 2014, which has been verified and is consistent with other AP reporting appears to show militants from the al-Qaida-inspired Islamic State of Iraq and the Levant (ISIL) with captured Iraqi soldiers wearing plain clothes after taking over a base in Tikrit, Iraq. The Islamic militant group that seized much of northern Iraq has posted photos that appear to show its fighters shooting dead dozens of captured Iraqi soldiers in a province north of the capital Baghdad. Iraq's top military spokesman Lt. Gen. Qassim al-Moussawi confirmed the photos’ authenticity on Sunday and said he was aware of cases of mass murder of Iraqi soldiers. (AP Photo via militant website)

This image posted on a militant website on Saturday, June 14, 2014, which has been verified and is consistent with other AP reporting appears to show militants from the al-Qaida-inspired Islamic State of Iraq and the Levant (ISIL) with captured Iraqi soldiers wearing plain clothes after taking over a base in Tikrit, Iraq. The Islamic militant group that seized much of northern Iraq has posted photos that appear to show its fighters shooting dead dozens of captured Iraqi soldiers in a province north of the capital Baghdad. Iraq’s top military spokesman Lt. Gen. Qassim al-Moussawi confirmed the photos’ authenticity on Sunday and said he was aware of cases of mass murder of Iraqi soldiers. (AP Photo via militant website)

The men were dressed in civilian clothing but were reported to be Iraqi soldiers. Tikrit and Mosul were seized by ISIL last week during which Iraqi Army soldiers were reported to have taken off their uniforms as they fled to avoid being identified as government loyalists.

Long War Journal reported that some of the ISIL fighters were seen holding U.S.-made M-16s that were likely seized from facilities that had previously been used by the Iraqi Army and police.

The Associated Press reported on Sunday that captions posted with the photos said that the killings were to avenge the death of an ISIL commander, Abdul-Rahman al-Beilawy.

TheBlaze cannot independently authenticate the photos or the video; however, Iraq’s top military spokesman, Lt. Gen. Qassim al-Moussawi, confirmed the photos’ authenticity to the AP and said he was aware of the mass murder of captured Iraqi soldiers.

A correspondent for Al Rai, a Middle East newspaper, linked via Twitter to this YouTube video which allegedly shows Iraqi soldiers sitting on the ground with their hands tied behind their back being forced to declare loyalty to the “Islamic State” before being executed.

Reuters reported on Saturday that the insurgent offensive had apparently slowed after days of advances and that the Iraqi Army regained some territory that had been seized by the Sunni militants last week.