Pope Francis has declared the death penalty "inadmissible" in an update of the most important guide to Catholic teaching, the Vatican announced on Thursday.

"The Church teaches, in the light of the Gospel, that 'the death penalty is inadmissible because it is an attack on the inviolability and dignity of the person'," the Holy See said in a statement.

The change to the catechism, a question and answer guide to what Catholics should think about a wide range of moral and social issues, also says that the Church will "work with determination" for the abolition of the death penalty worldwide.