Pope Francis prays for the fallen in Redipuglia. (Reuters)
Pope Francis prays for the fallen in Redipuglia war memorial.

Pope Francis has said that conflicts being waged "piecemeal" around the world could amount to a third World War.

In the homily of a Mass during a during a visit to Italy's largest war memorial Redipuglia, where more than 100,000 Italian soldiers who died in World War I are buried, Francis declared that "war is madness".

"Even today, after the second failure of another world war, perhaps one can speak of a third war, one fought piecemeal, with crimes, massacres, destruction," he said.

In recent months, Francis has made repeated appeals to end conflicts in Ukraine, Syria, Iraq, Gaza and parts of Africa.

"War is irrational; its only plan is to bring destruction: it seeks to grow by destroying," he said. "Greed, intolerance, the lust for power. These motives underlie the decision to go to war and they are too often justified by an ideology…" he said.

Pope condemns war

Francis' grandfather, who was from Piedmont in Italy, served with the Italian forces battling the Austro Hungarian empire in 1915-1917, adding poignancy to his tribute to those who fell in the conflict.

Before the Mass, he prayed at a nearby cemetery where 15,000 soldiers who died fighting for the Austro-Hungarians and their allies on the losing side of the Great War are buried.

"Today, too, the victims are many," killed in conflicts caused by "interests, geopolitical strategies, lust for money and power," the Pope said.

He lamented that the human toll of "senseless massacres" and "mindless wars".

"Humanity needs to weep, and this is the time to weep," he said.

Last month, the Pope said that it would be legitimate to use force against Islamic State (Isis) militants who have killed and displaced thousands in Syria and Iraq.

In the homily, he condemned the "plotters of terrorism".