Pope Francis stumbled and fell over as he began celebrating Mass in Poland earlier today.

The 79-year-old Pope immediately got back up and continued the Mass, during which he delivered a long sermon before tens of thousands of faithful gathered at the foot of the Jasna Gora monastery in the southern city of Czestochowa, proceeded as planned. 

The Pope was holding a thurible as he lost his footing after missing a step as he approached the altar during the Mass at the Black Madonna shrine to mark the 1,050th anniversary of the Baptism of Poland. He was helped up by several priests.

Pope Francis suffers from sciatica, a medical condition in which pain sometimes shoots down the leg from the lower back.

Asked if Francis had suffered any ill effects from the fall, the Vatican spokesman Greg Burke said: "The Pope is fine."

During his homily, the Pope said he prayed that Poles would have "the desire to leave behind all past wrongs and wounds, and to build fellowship for all, without ever yielding to the temptation to withdraw or to domineer".

Francis is in Poland for five days to celebrate World Youth Day. Tomorrow he will visit Auschwitz, the former Nazi concentration camp where he will meet survivors of the Holocaust.