Pope Leo XIV said on Friday he was elected new head of the world's 1.4 billion Catholics so the church can be a "beacon" to reach areas suffering a "lack of faith".

"God has called me by your election" to be a "faithful administrator" of the church so that it can be "an ark of salvation sailing through the waters of history and a beacon that illumines the dark nights of this world", Leo said in his first homily at the Sistine Chapel.

"There are many settings in which the Christian faith is considered absurd, meant for the weak and unintelligent... Settings where other securities are preferred, like technology, money, success, power or pleasure," he said during a mass for cardinals, according to a video broadcast by the Vatican.

"These are contexts where it is not easy to preach the Gospel and bear witness to its truth, where believers are mocked, opposed, despised or at best tolerated and pitied.

"Yet, precisely for this reason, they are the places where our missionary outreach is desperately needed," said the first US pontiff, a former missionary in Peru.

Leo's address to cardinals came less than 24 hours after his election as spiritual head of the 2,000-year-old institution.

He also warned against reducing Jesus to "a kind of charismatic leader or superman", in an apparent message to evangelical Christians.

"Today, too, there are many settings in which Jesus, although appreciated as a man, is reduced to a kind of charismatic leader or superman.

"This is true not only among non-believers but also among many baptised Christians, who thus end up living, at this level, in a state of practical atheism," he said. (AFP)