Turkey has recalled its ambassador to the Vatican for consultations in an escalating diplomatic row over Pope Francis' use of the word "genocide" to describe the massacres of Armenians by the Ottoman Empire during World War I.

"Our ambassador to the Vatican Mr Mehmet Pacaci is being recalled back to Turkey for consultations," the foreign ministry said in a statement on Sunday after earlier summoning the Vatican's envoy to Ankara to the ministry.

The ministry said in a statement that the pope's comments were "null and void" to the Turkish people.

The Turkish people would not recognise the pope's statement "which is controversial in every aspect, which is based on prejudice, which distorts history and reduces the pains suffered in Anatolia under the conditions of the First World War to members of just one religion", read the statement.

Francis made the speech at a mass in Saint Peter's Basilica to mark the 100th anniversary of the massacre of as many as 1.5 million Armenians.

"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," he said.

While Francis did not use his own words to describe the murders as genocide, it was the first time the term was spoken aloud in connection with Armenia by a head of the Roman Catholic Church in Saint Peter's Basilica.

The denial

Turkey accepts that many Christian Armenians died in clashes with Ottoman soldiers beginning in 1915, when Armenia was part of the empire ruled from Istanbul, but denies 1.5 million people were killed and that the incidents amounted to genocide.

Pope John Paul II and Armenian Apostolic Church Supreme Patriarch Kerekin II called it "the first genocide of the 20th century" in a joint written statement in 2001.

Francis, who has disregarded many aspects of protocol since becoming pope two years ago, is believed to have uttered the phrase before, but only in a private conversation with an Armenian delegation in 2013, prompting a strong protest from Ankara.

Francis' comments were published by Armenian President Serzh Sargsyan's office on Sunday.

"We are deeply grateful to His Holiness Pope Francis for the idea of this unprecedented liturgy ... which symbolises our solidarity with the people of the Christian world," Sargsyan said in a speech at a Vatican dinner on Saturday evening.