The Vatican began a new chapter on Tuesday with scandal-hit cardinal Tarcisio Bertone stepping down as right-hand man to Pope Francis and replaced by veteran diplomat Pietro Parolin.

The reform-minded new Secretary of State comes in as Francis mulls an overhaul of the way the Roman Catholic Church is run that could put an end to what the pope calls a "Vatican-centric" system.

The influential post is frequently referred to as the Vatican's equivalent of a prime minister.

Its incumbent can represent the pontiff on some occasions, and three have gone on to be popes.

Parolin himself was not present at the handover ceremony in the Vatican because he is undergoing a "small operation" and will take up his post "in a few weeks", the Vatican said in a statement.

"I would like to thank you for the courage and the patience with which you have lived through all the adversities you have faced. And they are many," the pope told Bertone at the ceremony.

Bertone defended his record, saying: "I see in Pope Francis not so much a revolution but a continuity with pope Benedict XVI despite differences in style and aspects of personal life."

He said he hoped that Parolin could "untie the knots that still prevent the Church from being in Christ at the heart of the world".