A new video released by Islamic State shows militants executing three Assyrian Christians and demanding a $14 million ransom for the release of more than 200 other Syrian hostages.

Wearing orange jumpsuits, the victims identify themselves as Dr Abdulmasih Aniya, Ashur Abraham and Bassam Michael. The three are from the towns of Tal Jazirah and Tal Shamiram in the Khabur river valley, al Hasakah province, in northern Syria.

As each man identifies himself, he says: "I am a Nazarene [a Christian]". They are then shot dead, before a militant demands that $14 million is paid for the release of the remaining hostages. According to the IB Times, one ISIS fighter in the video blames the Church for not protecting the men.

The victims were among Assyrians kidnapped by militants from 35 villages along the Khabur River in late February. Figures vary as to the exact number still missing, but it is believed to be around 230.

Initially, ISIS demanded a ransom fee of around $100,000 per hostage, totalling $23 million. When it became clear that the Assyrian community could not afford it, the amount was lowered.

Both the Assyrian Human Rights Network and the British-based Syrian Observatory for Human Rights said the latest video was likely filmed two weeks ago on Eid al-Adha.

A Demand for Action (ADFA), a group campaigning for the protection of religious minorities, has condemned the killing and called for international intervention.

"We condemn this latest act of barbarism in the strongest possible terms. The systematic ethno-religious cleansing of Assyrians/Syriacs/Chaldeans continues. They are helpless. They are children. They are women. They are somebody's father and brother," a statement from the group said.

"We plea and beg of the international community to intervene immediately. We have been driven out of our ancestral lands. We have been killed and crucified. The international community must act now to save lives of others kidnapped."

ADFA Founder Nuri Kino told Christian Today that the Church has been doing all it can to help those suffering under Islamic State.  "If we want to look at who carries responsibility for the current situation, then we don't need to look any further than the West and the international community, who have ignored our cries and pleas for help," he said.

"Christianity in the Middle East is becoming extinct. It cannot survive without a safe haven and international protection. As a people, the Assyrians/Chaldeans/Syriacs, who were among the first to embrace Christianity, are already on the endangered list. Without a safe haven in the Nineveh Plains, their ancestral home [and] our people will be a thing of the past."

Since the attacks in February, ISIS has besieged several ancient Assyrian sites, including the Iraqi city of Nimrud, the village of Khorsabad, and Hatra, a 2,000-year-old city. On Easter Sunday, militants destroyed the Virgin Mary Church in Tel Nasri, Khabur.

An ancient branch of Christianity, the Assyrian Church of the East has roots dating back to the 1st century AD. Assyrian Christians speak Aramaic, the language of Jesus, and have origins in ancient Mesopotamia – a territory which spreads across northern Iraq, north-east Syria and south-eastern Turkey.