The Vatican's new secretary of state, Archbishop Pietro Parolin, takes up his new appointment on 15 October. The Italian archbishop becomes the youngest cleric to occupy the post since the 1930s.

Pope Francis' choice of the 58-year-old archbishop as the Vatican's new secretary of state is the pontiff's most important appointment since his election in March.

The Vatican secretary of state acts as the Holy See's "prime minister", the pope's principal adviser and the head of the the Roman Curia, the powerful central administration of the Catholic Church.

Parolin, a senior Vatican diplomat from the Veneto region of northern Italy, replaces the 78-year old Cardinal Tarcisio Bertone, who was appointed in 2006 and whose mandate was extended twice by Pope Benedict before his retirement in February.

Parolin has worked in the Vatican's diplomatic corps since 1986, with roles within the Curia as well as nunciatures in Nigeria, Mexico and his current posting, Venezuela. His latest appointment is seen as an important move by Pope Francis to reform the Curia.

Parolin's predecessor Bertone was seen as a divisive, authoritarian figure whose critics accused him of cronyism and power politics. During the Sede Vacante transition period between the retirement of Benedict and election of Francis, Bertone presided as the Holy See adminstrator or camerlengo (chamberlain).

Parolin is the youngest cleric to occupy the post since 1930, when the 53-year old Eugenio Pacelli was appointed secretary of state before going on to become Pope Pius XII nine years later.