Pope Leo XIV celebrated his first Mass in the Sistine Chapel where he was elected less than 24 hours earlier, warning of the dangers caused by a lack of faith and hoping the Catholic Church could be a beacon lighting the world's "dark nights".

The pope's inauguration mass at St Peter's Square on Sunday, May 18 will be a far grander affair -- his first public mass as pope, during which he will preside before thousands of worshippers and world leaders.