The pope spoke hours after thousands of people attended a vigil in St. Peter's Square as part of a special day of prayer and fasting for peace in Syria.
"What's the point of fighting wars, many wars, if you're not capable of fighting this deep war against evil? There's no point! It's no good," he said.
Francis asked that people continue to pray for Syria, ensnarled in a civil war, as well as other countries in the region, including Lebanon, Iraq and Egypt, the Vatican Radio reported.
"I invite you to continue to pray so that the violence and devastation in Syria may cease immediately and that a renewed effort be undertaken to achieve a just solution to this fratricidal conflict," he said.