Pontiff’s comments are likely to anger Turkey, which denies that the killings 100 years ago during the fall of the Ottoman empire constituted genocide.
“Bishops and priests, religious women and men, the elderly and even defenceless children and the infirm were murdered,” the pope said.
Historians estimate that as many as 1.5 million Armenians were killed in a wave of violence that accompanied the fall of the Ottoman empire. Despite the massacre being formally recognised as a genocide by Italy and a number of other countries, Turkey refuses to accept it as such.
Reports in Turkey on Sunday said the Vatican’s ambassador to Ankara had been summoned to the foreign ministry to explain the pope’s remarks.
Although the pope chose to quote a predecessor rather than speak in his own words, he told Armenians there was a duty to remember to killings.
“We recall the centenary of that tragic event, that immense and senseless slaughter whose cruelty your forebears had to endure. It is necessary, and indeed a duty, to honour their memory, for whenever memory fades, it means that evil allows wounds to fester,” he said in St Peter’s Basilica.
During the mass Pope Francis also declared a 10th-century Armenian monk, St Gregory of Narek, a “doctor of the church”. The mystic and poet is celebrated for his writings, some of which are still recited each Sunday in Armenian churches.
The pope was joined at the Vatican by a number of Armenian dignitaries, including the president, Serž Sargsyan, and the head of the Armenian Apostolic church, Karekin II.
Theo van Lint, a Calouste Gulbenkian professor of Armenian studies at the University of Oxford, said allowing Armenian leaders to speak in St Peter’s Basilica was a strategic move.
“I think it’s very important to realise he gave space to the leaders, the heads of the Armenian church and Armenian Catholics, to fully give their view of events. It’s very clear that the pope accepts that it is a genocide,” van Lint told the Guardian.
He said the pontiff’s decision to refer to the mass killing of Armenians along with crimes perpetrated by Nazism and Stalinism gave the Vatican’s “highest sanction” to genocide recognition.
Igor Dorfmann-Lazarev, a researcher on Armenian history and culture at the School of Oriental and African Studies in London, said the ceremony demonstrated the pope’s efforts to put periphery Christian groups at the centre of the Catholic church.
“This is the first time that Armenia is the centre of attention of Catholic life and the Christian world. It’s meant to draw attention to the Christian east,” he said.
Francis’s use of the word “genocide” was unlikely to change relations between Armenia and Turkey, Dorfmann-Lazarev said, although it would raise diplomatic concerns at the Vatican.