Turkey is furious over Pope Francis's use of the word "genocide" in a mass marking the centenary of the slaughter of Armenians in the Ottoman Empire.
Hours after Francis spoke on April 12, Ankara said it was recalling its ambassador to the Vatican for consultations.
Turkish Prime Minister Ahmet Davutoglu said that "to read these sorrows in a one-sided way is inappropriate for the pope and the authority that he holds."
Foreign Minister Mevlut Cavusoglu said on Twitter that the pope's statement was "far from the legal and historical reality" and "cannot be accepted."
"Religious authorities are not the places to incite resentment and hatred with baseless allegations," he said.
Francis said the mass killings were "widely considered 'the first genocide of the 20th century,'" quoting a statement signed by Pope John Paul II and the Armenian patriarch in 2001.
It was the first time the term "genocide" has been used publicly in connection with Armenia by a head of the Roman Catholic Church in Saint Peter's Basilica.
The World War I-era mass slaughter and deportation of up to 1.5 million Armenians by Ottoman Turks is considered by many historians and several nations as genocide.
Turkey objects, saying that Armenians died in much smaller numbers and because of civil strife rather than a planned Ottoman government effort to annihilate the Christian minority.
Armenian President Serzh Sarkisian, who attended the mass along with Arminian church leaders, praised Francis for "delivering a powerful message to the international community."
"The words of the leader of a church with 1 billion followers cannot but have a strong impact," Sarkisian told AP.
Armenia has been campaigning for years to win international recognition of the mass killings as genocide.
Several European countries have officially recognized the massacre as genocide.
The United States has not followed suit, though 44 individual U.S. states have recognized the events as genocide and Republican and Democratic lawmakers introduced a resolution urging President Barack Obama to do so.
Armenia officially marks the anniversary on April 24.
The pope said the other two genocides of the last 100 years were "perpetrated by Nazism and Stalinism" but he also mentioned "more recently there have been other mass killings, like those in Cambodia, Rwanda, Burundi, and Bosnia."
Francis added, "It seems that humanity is incapable of putting a halt to the shedding of innocent blood."
During the special mass, Francis declared the revered 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.
Gregory, who lived around 950 to 1005, is considered one of the most important figures of medieval Armenian religious thought and literature.