Libyan National Army kills 20 blindfolded 'ISIS fighters', sparking concern [GRAPHIC PHOTOS]

A horrifying video that has taken the Internet by storm has shown 18 fighters purportedly belonging to the Islamic State group being shot in the back of their head by soldiers of the self-professed Libyan National Army (LNA).

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The supposed ISIS fighters, who are dressed in orange jumpsuits, are shown kneeling in rows and facing sway from their executioners.

The first three rows have five fighters each while the last row has three fighters.

The video shows the five fighters standing behind the first row with semi-automatic rifles shooting the captives from a point-blank range.

After the first row collapses, they move on to the second row to repeat their actions.

According to reports, the video was released by Khalifa Haftar and his self-styled Libyan National Army, who have declared victory in the eastern city of Benghazi.

Haftar, a former soldier under the Gaddafi regime has risen through the ranks to become the commander of the Libyan National Army.

Another video shows two fighters dressed in the same military fatigues also being shot dead by two members of the forces.

However, the act did not go down well with Human Rights Watch.

Besides criticising the act, it has asked Libyan officials to investigate the incident and dismiss the people involved in it.

"This latest mass execution, if confirmed, would be one more in a string of atrocities committed by members of the Libyan National Army forces and is yet another manifestation of how its members are taking the law into their own hands," Eric Goldstein, Middle East and North Africa deputy director for Human Rights Watch was quoted as saying by Reuters.