Pope Francis' characterisation of the Armenian massacres a hundred years ago as 'genocide' will "accelerate" moves for the ancient Christian cathedral of Hagia Sophia to be turned into a mosque again, according to a senior Turkish religious leader.

During a mass marking the centenary of the killing of around 1.5 million Armenians in circumstances often of extreme brutality, Francis said the event was "widely considered the first genocide of the 20th century". He was quoting Pope John Paul II, but his comment was seized upon by Turks who have never accepted that the massacres should be described as genocide.

Now the Grand Mufti of Ankara, Prof Mefail Hizli, has warned of possible repercussions. He said in a written statement: "Frankly, I believe that the Pope's remarks will only accelerate the process for Hagia Sophia to be reopened for [Muslim] worship."

He described the Pope's comment as a "modern reflection of the crusader wars launched in these lands for centuries", and said that it was a "one-sided take" on what had occurred.

Hagia Sophia, the Church of Holy Wisdom, was founded in AD360 by the Byzantines. The current church, one of the most remarkable church buildings in the world, was completed in AD 537 under Emperor Justinian. It was turned into a mosque after the Ottoman conquest of Constantinople in 1453 but was closed in 1931. It was turned into a museum in 1935 by the secular Turkish government, but under the increasingly Islamist government of Recep Tayyip Erdogan, nationalists have called for its re-opening as a mosque.

On April 10 a Muslim cleric recited the Qu'ran in the building for the first time in 85 years to mark the opening of an exhibition entitled "Love of the Prophet".

Turkish Deputy Prime Minister Bulent Arinc sparked speculation that its status would be changed when said in November 2013 that he hoped to change the status of the Hagia Sophia, saying it looked "sad" but hopefully would be "smiling again soon".

Turkey's Christian population is small and precariously placed, though Orthodox Christians regard the Ecumenical Patriarchate of Constantinople as the most prestigious of its Churches. Greece reacted furiously to Arinc's comment, saying such statements "are offending the religious feeling of millions of Christians". A decision to re-Islamise Hagia Sophia would be deeply controversial.