The Vatican's top envoy to the United Nations in Geneva recently endorsed military action against the Islamic State terror group, which he said fulfilled the Catholic Church's criteria as a legitimate target under its "just war" doctrine — but he has stopped short of saying the same of Syrian President Bashar al-Assad's government.

Archbishop Silvano Tomasi, who represents the Vatican's sovereign entity, the Holy See, commented on military action against the Islamic State on Friday in an interview with the Catholic website Crux. He spoke following the issuance of a joint statement at the UN Human Rights Council on the condition of Christians and other communities in the Middle East.

"We have to stop this kind of genocide," Tomasi remarked, referring to the abuses of the "so-called Islamic State," which is also known as ISIS, ISIL, and by its Arabic acronym Daesh. "Otherwise we'll be crying out in the future about why we didn't do something, why we allowed such a terrible tragedy to happen."

On Tuesday, the archbishop elaborated on the Vatican's uncharacteristic call to violent force in further comments to VICE News.

"Targeted are all the people who hold a different religious belief, or have a different cultural tradition, and the aim of the violence against them is their utter destruction," he said. "In the case of ISIS, it seems to me that the responsibility of the international community through the structures it has given itself for acting in emergencies, like that of the United Nations Security Council, is linked to the kind of genocide that is going on in the region."

'It's always surprising when you see church officials calling explicitly for the use of force.'

Throughout their campaign in the Middle East, Islamic State militants have massacred and carried out a litany of other war crimes against unarmed Christians despite their qualifying as "people of the book" — a protected class under Islamic law, which the extremist group claims to follow. Other religious minorities like the Yazidis have also been viciously persecuted.

Last month, the Islamic State released a video depicting the beheadings of 21 Egyptian Coptic Christian migrant workers on the Mediterranean shore of Libya. The grotesque images were followed by a promise to conquer Rome, within which the Vatican City is ensconced. The Holy See's security forces are vigilantly mindful of plots by the Islamic State to assassinate Pope Francis.

"It's always surprising when you see church officials calling explicitly for the use of force," Joseph Capizzi, a professor of moral theology at the Catholic University of America, told VICE News. "But we are dealing with something unprecedented. This is the singling out of innocent populations."

Government and aligned forces in both Iraq and Syria have killed civilians and been accused of committing war crimes and human rights abuses while ostensibly fighting Sunni rebel groups like the Islamic State and al-Nusra Front, an al Qaeda affiliate. In Syria, Assad's government is by most estimates responsible for the vast majority of civilian deaths in that country's four-year civil war. They have not, however, widely publicized their morbid exploits in the manner of the Islamic State.

Christian theologians say that Tomasi's singling out of the Islamic State does not rule out possible support for international action against Assad's regime under the doctrine of just war, which holds that "legitimate defense by military" is morally justifiable under a narrow set of circumstances, including to help save innocent lives that are in imminent danger. But Tomasi declined to respond when VICE News asked if the Vatican was considering whether Assad's crimes and the situation in Syria might similarly justify an international intervention.

"This is the most complicated factor here," Kevin Ahern, a theologian and professor of religious studies at Manhattan College, told VICE News. "The Holy See has been critical of the Syrian government in the past. But the Christians in Syria have largely aligned themselves — or were manipulated by — the 'secular' Assad government."

"We are seeing ancient peoples and cultures vanishing," he added. "The Iraqi Chaldean Catholic Church, for example, still uses the language that Jesus spoke in their prayers. It's an ancient culture and we are seeing it, along with other minority groups, disappear. Something has to be done. There is no excuse for the crimes committed by the Syrian government."

According to the official catechism of the Catholic Church, which outlines its theological instructions and doctrine, "the damage inflicted by an aggressor on the nation or community of nations must be lasting, grave, and certain" to justify war for the "common good." The conditions also stipulate that military action must have "serious prospects of success" and that "the use of arms must not produce evils and disorders graver than the evil to be eliminated."

A coalition led by the United States has launched more than 2,600 airstrikes against suspected extremist targets in Iraq and Syria over the past year. Last summer, as the coalition was beginning its campaign, Pope Francis spoke to reporters about the rationale justifying an intervention against Islamist militants in Iraq.

"In these cases, where there is an unjust aggression, I can only say that it is legitimate to stop the unjust aggressor," the pontiff said.

Related: How the US Created the Islamic State. Watch the video here.

This position, echoed by Archbishop Tomasi, stands in contrast to the late Pope John Paul II's vocal opposition to the American invasion of Iraq in 2003 — a military initiative that many geopolitical observers have argued set the stage for the evolution of the Sunni insurgency that is roiling the region.

"The critical difference between the 2003 invasion of Iraq and the present situation is that in the first instance the military action started a period of violence, while in the present case, if there is a coordinated use of force, the goal is to stop the ongoing atrocities," Tomasi explained to VICE News. "Besides, it is difficult for the international community to dialogue and to attempt to resolve the situation with a non-state group of extremists who do not abide by any internationally accepted rule."

J. Patrick Hornbeck II, a theology professor at Fordham University, noted that this is a wrinkle in the application of just war doctrine to the situation in Iraq and Syria — namely that belligerents like the Islamic State are often not, or only claim to be, part of a recognized state.

This same distinction, scholars of Islamic law have told VICE News, render the terror group's theological justification for its own actions void. Because the group's self-declaration of a caliphate is illegitimate, Islamic State leaders are not in a position to interpret Islamic law in the perverse manner that they have to justify their atrocities.

Tomasi noted that military action would only be proper if carried out under the auspices of the United Nations.

"In the end, the grave decision to use force rests with states, who have the obligation to ensure that conditions for peace exist in their own territory and throughout the world," he said. "War is always a disaster."