The leader of the Catholic Church, Pope Francis I, has tripped and fallen while performing an open air mass at the shrine of Jasna Gora, Poland's holiest site today (28 July).

Deep in thought and possibly weighed down by his incense burner, the pontiff took a tumble near the altar after missing a step. Priests around him rushed to help him up and straightened his robe, the Associated Press reported.

Francis, undeterred by his brush with gravity, continued the service to the tens of thousands of faithful gathered at the foot of the Jasna Gora monastery in the city of Czestochowa.

Francis praised a legacy of steadfast Catholic faith in Poland as he urged inhabitants of the country to remain true to their faith. The mass in the southern city was held in celebration of the 1,050th anniversary this year of Poland's acceptance of Roman Catholicism.

The Argentine pope has sought to heal divisions in Europe and particularly in Poland over the course of his visit, combating anti-Muslim and anti-refugee rhetoric. He also addressed recent acts of terror, particularly in France, where on 26 July French Catholic priest Father Jacques Hamel was killed by militants linked to the Islamic State (Isis/Daesh).

Francis said the "world is at war" as he arrived in Poland on Wednesday (27 July) for the World Youth Day — an international Catholic event focused on faith and youth. He clarified that the war was not over religion, but it was a clash over "interests, money, resources".