Pope Francis has angered Turkey by using the term"genocide" to describe the killing of up to 1.5 million Armenians by the Ottoman Turks.
Speaking at a mass in Saint Peter's Basilica to mark the centenary of the event, Pope Francis noted that humanity had experienced "three massive and unprecedented tragedies" in the past 100 years.
"The first, which is widely considered 'the first genocide of the 20th Century', struck your own Armenian people," he said to the congregation.
"It is necessary, and indeed a duty, to honour their memory, for whenever memory fades, it means that evil allows wounds to fester. Concealing or denying evil is like allowing a wound to keep bleeding without bandaging it," the Pope said.
The Pope's comments have infuriated Turkey, who vehemently says that the figures have been inflated and consequentially, deny that the killings constitute genocide. Turkey says that between 300,000-500,000 Armenians and a similar number of Turks died when the former rose up against the latter.
Last year, current Turkish president, Recep Tayyip Erdoğan offered his sympathies to the grandchildren of slain Armenians.
Armenia and historians maintain that up to 1.5 million people were massacred by Ottoman forces in 1915 as the empire crumbled and Armenia has consistently sought to define the slaughter as genocide.
Pope Francis said the other two genocides of the 20th century were "perpetrated by Nazism and Stalinism" and added: "More recently there have been other mass killings, like those in Cambodia, Rwanda, Burundi and Bosnia. It seems that humanity is incapable of putting a halt to the shedding of innocent blood."
The Vatican has previously incurred Turkish fury after Pope John Paul II used the term "genocide" in a joint statement signed with the Armenian patriarch in 2000.
Kardashians mark anniversary
Last week, TV celebrities, Kim and Khloe Kardashian visited their ancestral home in Armenia to mark the anniversary with Kim's husband Kanye and daughter North West.
They met with Armenia's Prime Minister Hovik Abrahamyan, who praised their efforts to push for "international recognition and condemnation of the Armenian genocide".
A government statement said: "The Kardashians apologised for not speaking Armenian, but said they are learning their native language."
"They pledged to continue the struggle for international recognition and condemnation of the Armenian genocide."