VATICAN CITY — Pope Francis on Sunday honored the 100th anniversary of the slaughter of Armenians by calling it “the first genocide of the 20th century,” a politically explosive declaration that will certainly anger Turkey. Francis, who has close ties to the Armenian community from his days in Argentina, defended his pronouncement by saying it was his duty to honor the memory of the innocent men, women, children, priests and bishops who were “senselessly” murdered 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 Sunday in the Armenian Catholic rite in St. Peter's Basilica honoring the centenary. Historians estimate that up to 1.5 million Armenians were killed by Ottoman Turks around the time of World War I, an event widely viewed by scholars as the first genocide of the 20th century. Turkey, however, refuses to call it a genocide and has insisted that the toll has been inflated, and that those killed were victims of civil war and unrest. Turkey's embassy to the Holy See canceled a planned news conference for Sunday, presumably after learning that the pope would utter the word “genocide” over its objections. Requests for comment went unanswered and there was no official word on Sunday from the government in Ankara. Several European countries recognize the massacres as genocide, though Italy and the United States, for example, have avoided using the term officially given the importance they place on Turkey as an ally. The pope, too, places great importance in its relationship with the moderate Muslim nation, especially as it demands Muslim leaders condemn the slaughter of Christians by Muslim extremists in neighboring Iraq and Syria. But Francis' willingness to rile Ankara with his words showed once again that he is willing to take diplomatic risks for issues he cares deeply about. 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. Francis is not the first pope to call the massacre a genocide. In his remarks, Francis cited a 2001 declaration signed by St. John Paul II and the Armenian church leader, Karenkin II, which said the deaths were considered “the first genocide of the 20th century.” Emeritus Pope Benedict XVI, whose ties with Turkey and the Muslim world were initially strained, avoided using the “g-word” during his pontificate. While Francis was archbishop of Buenos Aires, the former Cardinal Jorge Mario Bergoglio referred to the Armenian “genocide” on several occasions, including three separate citations in his 2010 book “On Heaven and Earth.” The definition of genocide has long been contentious. The United Nations in 1948 defined genocide as killing and other acts intended to destroy a national, ethnic, racial or religious group, but many dispute which mass killings should be called genocide. In his remarks on Sunday, Francis said the Armenian slaughter was the first of three “massive and unprecedented” genocides last century that was followed by the Holocaust and Stalinism. He said other mass killings had followed, including in Cambodia, Rwanda, Burundi and Bosnia. “It seems that the human family has refused to learn from its mistakes caused by the law of terror, so that today too there are those who attempt to eliminate others with the help of a few and with the complicit silence of others who simply stand by,” he said. Francis has frequently denounced the “complicit silence” of the world community in the face of the modern-day slaughter of Christians and other religious minorities by extremists. The Armenians have been campaigning for greater recognition of the genocide in the lead-up to the centenary, which will be formally marked on April 24. Sunday's Mass was concelebrated by the Armenian Catholic patriarch, Nerses Bedros XIX Tarmouni, and was attended by Armenian Orthodox church leaders as well as Armenian President Serzh Sargsyan, who sat in a place of honor in the basilica. Francis also honored the Armenian community at the start of the Mass by pronouncing a 10th-century Armenian mystic, St. Gregory of Narek, a doctor of the church. Only 35 people have been given the title, which is reserved for those whose writings have greatly served the universal church. The Mass, which followed the Armenian Catholic rite, was rich in traditional Armenian music, with haunting hymns used at key points. Children dressed in traditional costumes presented the gifts at the altar, which was bathed in a cloud of incense. — AP