WARNING: GRAPHIC CONTENT

The men are understood to be ISIS fighters who were killed by the Libyan Army

Executioners walk up to a row of prisoners and shoot them dead with rifles

Killers then turn on their heels and walk back before the sequence is repeated

A shocking video has emerged showing 18 prisoners in orange jumpsuits getting shot in the back of the head from point-blank range in summary executions in Libya.

The men, understood to be ISIS fighters, are shown kneeling in four rows and facing away from their killers.

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Executioners can be seen walking up slowly behind their targets before firing a spray of bullets from what look like semi-automatic assault rifles into the backs of their heads before another line of killers repeat the sequence.

It comes amid tensions between jihadists and Libyan forces in Benghazi after strongman Khalifa Haftar - a former soldier under the Gaddafi regime who has risen through the ranks to commander of the Libyan National Army - declared victory in the eastern city.

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Executioners, thought to be from the Libyan National Army, take aim at their targets - supposedly ISIS fighters in the country

The killers spray their targets with bullets long after they have fallen to the ground in a heap

Eighteen blindfolded prisoners in Guantanamo Bay-style jumpsuits line up to face their deaths

The gruesome video, seen by MailOnline, shows all 18 men in orange jumpsuits falling to the floor after being shot, but it it not clear who is pulling the trigger and giving the orders.

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It is claimed by the Libyan Express the commander of the eastern Saiqa Force of Operation Dignity Mahmoud Al-Werfalli conducted the massacre.

He was also said to have ordered the killings by the Libyan Observer, who reported he had been promoted by Haftar, leader of the Libyan National Army, for his alleged role in killing policemen in May.

It is understood those killed were ISIS fighters in Libya, according to Al Jazeera, who again claimed it was Al-Werfalli reading the charges before his proteges shoot the detainees dead.

In the video, a man can be seen reading from a piece of paper and men in military uniform can be seen walking up to their targets, taking one each, and unleashing a flurry of bullets on the command of their leader.

The kneeling men fall to the ground face-first, which doesn't stop the gunmen from shooting.

Eventually, they turn on their heels and walk back together in a line before a new set of executioners walk forward and kill the next line of prisoners.

A man in an orange jumpsuit located in the second line appears to fall forward in an attempt to fool the executioners, but he is dragged back onto his knees and callously shot in the head in the second round of killings.

The sequence continues until all 18 men are dead.

The first row of prisoners are taken out by the first line of executioners in the video dated July 17

Five prisoners lay face-down in the dirt after being shot in the back of the head at point-blank range

Dust rises from the ground in the desert as the executioners stand behind the men they have killed

Executioners holding up their semi-automatic assault rifles before pulling the trigger and killing their targets

The video is dated July 17, which means it would have come just days after the UN's human rights spokeswoman Liz Throssell said called for the Libyan National Army (LNA) which controls the eastern part of the country to investigate summary executions of prisoners.

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The UN's human rights body and voiced concern at the fate of those still in their custody.

The LNA is pushing to expand its presence in central and southern Libya, where it has been vying for control with forces linked to the UN-backed government in Tripoli and other opponents.

LNA leader Khalifa Haftar has gained ground with Egyptian and Emirati support, and Western states say Haftar must be part of any solution to Libya's conflict

UN human rights spokeswoman Liz Throssell said: 'We are deeply concerned that, after recent fighting in Benghazi, people taken prisoner by members of the Libyan National Army, which effectively controls eastern Libya, may be at imminent risk of torture and even summary execution.

'Reports have suggested the involvement of Special Forces, a unit aligned with the LNA, in torturing detainees and summarily executing at least 10 captured men.'

A member of the self-styled Libyan National Army, loyal to the country's east strongman Khalifa Haftar, rides in a tank as it drives down a street through the rubble in Benghazi's central Akhribish district on July 19, 2017 following clashes with militants

Smoke billows from buildings during clashes between members of the self-styled Libyan National Army, loyal to the country's east strongman Khalifa Haftar, and militants in Benghazi's central Akhribish district on July 19, 2017

A picture shows a damaged building in Benghazi's central Akhribish district on July 19, 2017. Libyan military strongman Khalifa Haftar on July 5, 2017, announced the "total liberation" of second city Benghazi, which was overrun by jihadists three years ago

The Libyan National Army announced last March that it would conduct investigations into alleged war crimes but has not shared any information, Throssell said.

'We urge the LNA to ensure there is a full, impartial investigation into these allegations,' she said.

Throssell also called on the group to suspend Mahmoud al-Werfalli from his duties as a Special Forces field commander pending the conclusion of such an investigation.

A video circulating on social media in March allegedly showed al-Werfalli shooting dead three men who were kneeling and facing a wall with their hands tied behind their backs, Throssell said.

In June, two further videos appeared to show summary executions carried out by LNA fighters on his orders.

'One of these videos, which emerged on 9 June, shows four men kneeling with their hands tied behind their backs who are shot dead as al-Werfalli watches,' she said.

'The latest video, which was posted on social media this month, seems to shows LNA fighters kicking and taunting prisoners, while al-Werfalli is apparently heard accusing two men who have their hands tied behind their backs of belonging to terrorist groups,' she said.

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The LNA has declined comment on the images.