VATICAN CITY -- Pope Francis has condemned "deplorable acts of terrorism and violence" in Munich and Kabul that have left dozens dead in recent days.

Addressing a crowd in St. Peter's Square on Sunday, Francis urged believers to join his prayers, saying that "as much as the difficulties seem insurmountable and dark the prospects of peace and security, our prayers must be that much more insistent."

A German-Iranian 18-year-old that police said was obsessed with mass-shootings killed nine people, mostly teens, in a shopping mall shooting spree in Munich on Friday, while a suicide bomber killed at least 80 people during a peaceful demonstration in Kabul on Saturday.