Pope Leo, the first U.S.-born leader of the global Catholic Church, prayed on Sunday that God would "stop the pandemic of arms" after a mass shooting on August 27 at a Minnesota Catholic school that killed two children.

"Our prayers (go) for the victims of the tragic shooting during a school Mass in the American state of Minnesota," Leo, speaking in English, said in a weekly prayer with crowds in St. Peter's Square.

"Let us plead God to stop the pandemic of arms large and small, which infects our world," said the pope.

Leo was elected pope by the world's cardinals in May after the death of the late Pope Francis. He has shown a different style to his predecessor, rarely speaking off the cuff and usually preferring a more cautious tone in his public appeals.

Sunday's appeal was also a rare instance of the pope addressing a world event in his native English. Leo usually prefers to use Italian, the language of the papacy.