An exodus of Christians is currently underway as millions of people are leaving their homes in Syria for fear of their lives amid the escalating conflict involving the extremist group Islamic State of Iraq and Syria (ISIS), rebel fighters and government forces.

A Church leader, however, is appealing to young Christians to stay in the strife-torn country to prevent Christianity from disappearing in Syria.

In an open letter, Melkite Greek Catholic Patriarch Gregorios III lamented how more and more young Christians are leaving Syria due to the conflict.

"The almost communal wave of youth emigration, especially in Syria, but also in Lebanon and Iraq breaks my heart, wounding me deeply and dealing me a deadly blow," Gregorios said.

The senior Catholic leader said this exodus of Christians out of Syria is threatening the future of Christianity in the area.

"Given this tsunami of emigration ... what future is left for the Church? What will become of our homeland? What will become of our parishes and institutions?" Gregorios asked.

Gregorios acknowledged that staying in Syria will entail some risks, but encourage the Syrian Christian youth to hold on to their faiths.

"Despite all your suffering, stay! Be patient! Don't emigrate! Stay for the Church, your homeland, for Syria and its future! Stay! Do stay," the Catholic leader said.

For four years now, Christians in Syria have been caught in the crossfire between President Bashar al-Assad's forces and rebels who want to oust him. Al-Assad's forces have launched airstrikes that have destroyed several churches in Syria.

Christians in Syria have also been experiencing persecution from ISIS militants, who have kidnapped hundreds of Assyrians for ransom or to turn them into sex slaves.

Bishop Yatron Koliana of the Assyrian Church of the East in Lebanon estimates that some 15,000 Christian families are under threat from ISIS militants.

Koliana said most displaced Assyrians want to go back to their homeland and are hoping for help from "strong countries."

"We very much hope that countries such as Russia and the United States will hear our call for help from their Christian brothers in the Middle East," the bishop said.