The Turkish president has sharply criticised Pope Francis for describing the mass killing of Armenians under Ottoman rule in WW1 as "genocide".

Recep Tayyip Erdogan said he condemned the Pope and warned him to "not repeat this mistake".

Turkey rejects the use of the term genocide to describe the killings, arguing it was a civil war in which both sides died.

It is calling for a joint study by historians of what happened.

Turkey recalled its envoy to the Vatican after Pope Francis made the comments on Sunday at a Mass at St Peter"s Basilica, attended by the Armenian president and the head of the Armenian Apostolic Church, Karekin II.

The Pope said that humanity had lived through "three massive and unprecedented tragedies" in the last century.

 Mr Erdogan said on Tuesday that when political or religious leaders played the role of historians, what resulted was "delirium, not fact".

"Hereby, I want to repeat our call to establish a joint commission of historians and stress we are ready to open our archives. I want to warn the Pope to not repeat this mistake and condemn him."