The Pope's comments have come as fighting resumes in Syria. Pope Francis is meeting religious leaders in Assisi - the birthplace of his papal namesake, Saint Francis.
Pope Francis held peace talks with religious leaders and victims of war in the Italian town of Assisi on Tuesday, broaching issues such as religious extremism and escalating violence around the world.
"There is no God of war," the Argentine said, denouncing extremist factions waging war in the name of God. "As we pray today, it would be good if we all felt shame, shame that humans, our brothers and sisters, are capable of doing this."
The 79-year-old Pope's comments come as fighting resumed in Syria after the ceasefire agreement, brokered by the United States and Russia, collapsed.
Before flying to Assisi, the Pope reminded the developed world that the string of deadly jihadist attacks it has endured did not compare to the devastation in other parts of the world.
"We are frightened… by some terrorist acts" but "this is nothing compared to what is happening in those countries, in those lands where day and night bombs fall," he said at a morning mass in the Vatican.
Pope Francis arrived in the medieval Italian hillside town on Tuesday for the annual World Day of Prayer event. There, he held talks with a number of faith leaders from across different religions, as well as 12 refugees who have fled conflicts in Nigeria, Eritrea, Mali and Syria.
All representatives also gathered to pray for peace and remember victims of war.
Faith leaders in attending the event include Archbishop of Canterbury Justin Welby and the Orthodox Patriarch of Constantinople Bartholomew I. There were also a number of Muslim, Jewish and Hindu representatives, as well as the Supreme head of the Tendai Japanese school of Mahayana Buddhism.
Overall, around 500 representatives from different religions have been taken part in a series of roundtable discussions with lay people since Sunday. Topics have reportedly ranged from religious violence to the migration crisis and climate change.
The Pope also ate with Syrian refugees Mohanad and Nour Zanbou and their daughter. The family fled Syria at the end of 2014 after enduring more than "three years of war terror."
A religious tradition
World Prayer Day was established by Pope John Paul II and is held annually in the central Italian town.
This is the Pope Francis' second visit to Assisi in as many months. His papal namesake, Saint Francis, was born and found God in the town. Saint Francis renounced his wealth for a life of poverty and to preach tolerance, peace and gentleness.
The Pope, whose birth name is Jorge Mario Bergoglio, adopted the papal name Francis to honor the Christian friar and emulate the saint's devotion to peace and forgiveness.
Since beginning his papacy in 2013, Francis has decried war and conflicts. These conflicts are, in essence, a "Third World War in segments," he said.
dm/jil (AFP, AP)