Pope Francis, in a visit to a military cemetery on the day Catholics remember their dead, on Tuesday urged arms manufacturers to "stop", because war "swallows up the children of the homeland".

On All Souls Day, Francis said a Mass at the French military cemetery in Rome, with its rows of white crosses the burial place of about 1,900 French and Moroccan soldiers killed in World War Two.

Francis, who visits a cemetery each year on the day of remembrance, laid white roses and stopped to pray at some of the tombs and mentioned that one read "Unknown, Died for France, 1944."

"Not even a name. But in the heart of God there are all our names. This is the tragedy of war," he said in an improvised sermon.

"I am sure that all of these who were called to defend the homeland and went with good will are with the Lord," Francis said.

"But ... do we fight enough so that there are no wars, so that there are no economies of countries that are strengthened by the weapons industry?" he said.

"These tombs are a message of peace. Stop brothers and sisters, stop. Stop, arms manufacturers, stop!" he said, calling those buried at the cemetery among the many "victims of war, which swallows up the children of the homeland".

Francis has made many calls for disarmament and has said that nuclear weapons should be banned because even their possession for deterrent reasons is "perverse" and indefensible.

When the location of the Mass was announced last month, an Italian group protested, saying the choice was an offence to victims of Moroccan soldiers, known as Goumiers, an auxiliary unit of the French military when France was still the colonial power.

They committed many random murders and raped many Italian women in the countryside between Naples and Rome as allied forces moved up the Italian peninsula.

One such incident was immortalized in the 1960 neo-realist film by Vittorio De Sica "Two Women," starring Sophia Loren, which told the story of a woman and her daughter who were both raped by Moroccan soldiers south of Rome.