Pope Francis has often framed the upsurge in violence around the globe in terms of a "third World War" being waged piecemeal through crimes, massacres, religious persecution and the destruction of cultural sites.
On Saturday, he told the Italian Bishops Conference TV2000 that the attacks in Paris were "part" of that, adding "there are no justifications for these things."
Pope Francis said he was "moved and saddened" by the attacks in Paris but confessed that "I don't understand these things. They are difficult to understand, carried out by human beings."
The pope, speaking in a heavy and measured voice, made the comments in a phone call broadcast on the conference.
Asked if there can be a religious justification for such attacks, Francis responded: "Religious and human. This is not human."
Francis says he was "close to the much-beloved people of France, I am close to the relatives of the victims and I pray for all of them."
At least 127 people died in Friday night's rampage in Paris. The Islamic State group has claimed responsibility.