Pontiff particularly recalled his trip to a camp on the Greek island of Lesbos last year, where he met a refugee from the Middle East.
"I don't know if he managed to leave that concentration camp, because refugee camps, many of them, are of concentration (type) because of the great number of people left there inside them," the pope said.
At the same time, Pope Francis commended the activity of countries helping refugees and thanked them for "bearing this extra burden, because it seems that international accords are more important than human rights".
It is noteworthy that the statement of Pope Francis upset the American Jewish Committee (AJC), which later urged the pope "to reconsider his regrettable choice of words" for using the term concentration camp.
"The conditions in which migrants are currently living in some European countries may well be difficult, and deserve still greater international attention, but concentration camps they certainly are not," David Harris, Head of the AJC, commented.
Harris stressed that nazis and their allies used concentration camps in order to exterminate millions of people during WWII, thus it is not comparable to the tragedy.