Pope Francis has denounced what he calls the "great powers" of the world for failing to act when there was intelligence indicating Jews, Christians, homosexuals and others were being transported to death camps in Europe during World War II.

He also decried "how many Christians suffered" and died in gulags later in Russia under the Stalin dictatorship.

The pope's harsh assessments came in impromptu remarks during his visit to Turin, northern Italy, when he told young people he understands how they find it hard to trust the world.

Francis said: "The great powers, they divided Europe like a cake" in the 1930s and 1940s and lamented that in today's world "everything is done for money."

He also lamented the hypocrisy of those advocating peace while also manufacturing or selling arms.