Pope Francis is greeted by the head of Armenia's Orthodox Church Karekin II April 12, 2015. Pope Francis called the slaughter of Armenians by Ottoman Turks "the first genocide of the 20th century" and urged the international community to recognize it as such, sparking a diplomatic rift with Turkey. (Gregorio Borgia/AP)

Pope Francis on Sunday called the slaughter of Armenians by Ottoman Turks “the first genocide of the 20th century” and urged the international community to recognize it as such, sparking a diplomatic rift with Turkey at a delicate time in Christian-Muslim relations.

Armenian President Serge Sarkisian, who was on hand to mark the 100th anniversary of the slaughter at a Mass in St. Peter’s Basilica, praised the pope in an interview. But Turkey, which has long denied that a genocide occurred, recalled its ambassador to the Holy See in protest.

“The pope’s statement, which is far from historic and legal truths, is unacceptable,” Turkish Foreign Minister Mevlut Cavusoglu tweeted. “Religious positions are not places where unfounded claims are made and hatred is stirred.”

Francis defended his pronouncement by saying it was his duty to honor the memory of the innocent people “senselessly” killed by Ottoman Turks.

“Concealing or denying evil is like allowing a wound to keep bleeding without bandaging it,” he said at the start of a Mass in the Armenian Catholic rite honoring the centenary.

The Turkish Foreign Ministry summoned the Vatican ambassador to Turkey Antonio Lucibello over Pope Francis’s remarks. (Str/EPA)

In a subsequent message, Francis called on all heads of state and international organizations to recognize the truth of what transpired to prevent such “horrors” from happening again and to oppose such crimes “without ceding to ambiguity or compromise.”

Historians estimate that Ottoman Turks killed up to 1.5 million Armenians around the time of World War I, an event widely viewed by scholars as the first genocide of the 20th century.

Turkey, however, has insisted that the toll has been inflated and that those killed were victims of civil war and unrest, not genocide. It has fiercely lobbied to prevent countries from officially recognizing the massacre as genocide.

Several European countries recognize the slaughter as genocide, though Italy and the United States, for example, have avoided using the term officially, given Turkey’s importance as an ally.

Vatican ambassador to Turkey Antonio Lucibello watches Pope Francis and Turkish President Recep Tayyip Erdogan walk together during a welcoming ceremony in Ankara, Turkey, November 28, 2014. (Str/EPA)

The Holy See, too, places great importance in its relationship with the moderate Muslim nation. But Francis’s willingness to rile Ankara with his words showed again that he has few qualms about taking diplomatic risks for issues close to his heart. He took a similar risk by inviting the Israeli and Palestinian presidents to pray together for peace at the Vatican — a summit that was followed by the outbreak of fighting in the Gaza Strip.