"In the past century, our human family has lived through three massive and unprecedented tragedies," the Pope said at a Mass at St. Peter's Basilica to commemorate the 100th anniversary of the Armenian massacres.
"The first, which is widely considered 'the first genocide of the 20th century,' struck your own Armenian people," he said, referencing a 2001 declaration by Pope John Paul II and the head of the Armenian church.
His use of the term genocide -- even though he was quoting from the declaration -- upset Turkey.
The nation recalled its ambassador to the Vatican for "consultations" just hours after Francis' comments, the Turkish Foreign Ministry said. Earlier, Turkey summoned the ambassador from the Vatican for a meeting, Turkish state broadcaster TRT reported.
Turkey's former ambassador to the Vatican, Kenan Gursoy, told CNN in a telephone interview that while it is the first time Turkey has summoned its ambassador home from the Vatican, "This does not mean that our diplomatic ties with the Vatican are over."
"Since this is a situation that we do not approve of, as a first reaction, (the ambassador) is summoned to get consultation," Gursoy said, adding that the Pope's use of the word "genocide" was "a one-sided evaluation."
In a tweet Sunday on his official account
, Turkey's Foreign Minister Mevlut Cavusoglu called the Pope's use of the word "unacceptable" and "out of touch with both historical facts and legal basis."
"Religious offices are not places through which hatred and animosity are fueled by unfounded allegations," the tweet reads.
This consternation over the use of the word 'genocide' occurs regularly. And Armenians are equally upset, when Turkey protests it. Armenian Foreign Minister Edward Nalbandian rebuked Turkey.
"We are in a situation in which Turkey speaks a different language from the rest of the international community and it seems that it doesn't understand that it is speaking a different language," he said to Italian News Agency Adnkronos.
"During these past days there have been several international organizations that adopt resolutions or issue statements that recognize the Armenian genocide and that appeal to Turkey to make this step," he said. "The Pope's statement are in this context of universal value. When Turkey is able to understand this, it will be able to understand what the International community and big personalities (or better translations 'leaders') are saying."
More than a million massacred
Armenian groups and many scholars say that Turks planned and carried out genocide, starting in 1915, when more than a million ethnic Armenians were massacred in the final years of the Ottoman Empire.
Turkey officially denies that a genocide took place, saying hundreds of thousands of Armenian Christians and Turkish Muslims died in intercommunal violence around the bloody battlefields of World War I.
The Armenian government and influential Armenian diaspora groups have urged countries around the world to formally label the 1915 events as genocide. Turkey has responded with pressure of its own against such moves.
Pope Francis said Sunday that "Catholic and Orthodox Syrians, Assyrians, Chaldeans and Greeks" were also killed in the bloodshed a century ago.
He said Nazism and Stalinism were responsible for the other two "massive and unprecedented tragedies" of the past century.