Addressed to the "nation of the cross," the 29-minute long video, uploaded on Sunday and produced by the Islamic State's media wing, al-Furqan, details the schisms that occurred in the Christian faith and which led to the formation of the Ethiopian Orthodox church, and shows the self-styled Caliphate's destruction of churches and Christian symbols throughout the regions under its control.

Footage is then shown of two groups of dark-skinned captives led by armed militants. One group, numbering 12, is held by militants on Libya's northern coast and the other, numbering 16, held by a fighters in Libya's southern desert interior.

A fighter, speaking in American accented English then addresses Christians, whom he calls the "nation of the cross" and threatens perpetual conflict unless non-Muslims are prepared to live under Islamic law and pay the "jizya", or religious tax.

The footage then shows the graphic decapitation of the first group on the beach, as well as the shooting deaths of the 16 men in the south.

It is not immediately clear who the captives were, but a caption claims they are members of "the hostile Ethiopian Church."

This is not the first time that the Islamic State's North African branch has specifically targeted Christians.

In February, 21 Egyptian Copts were abducted and their beheading was filmed in a similar manner.

A caption on that video read: "The people of the cross, followers of the hostile Egyptian church."