Pope apologises for Vatican role in justifying slavery

In a major text warning about the risk of "new forms of slavery" behind the digital economy, Leo said Church institutions owned slaves until the Middle Ages.

"In the early modern period, the Apostolic See of Rome, responding to requests from sovereigns, intervened several times in order to regulate and legitimize forms of subjugation, and, in certain cases, the enslavement of 'infidels'," he wrote.

It was only in the 19th century that "a formal, absolute and universal condemnation of slavery was clearly articulated," he said in the text, "Magnifica Humanitas" (Magnificent Humanity).

"For this, in the name of the Church, I sincerely ask for pardon," Leo wrote.

Popes have in the past have apologised for the involvement of Christians in the slave trade.

John Paul II denounced it in 1992 before issuing a sweeping request for forgiveness for historical injustices in 2000.

Pope Francis also repeatedly denounced contemporary forms of slavery.

But Leo's words went further by mentioning the Vatican's direct involvement in legitimising slavery.

"It is true that past events cannot be judged anachronistically, as though the moral criteria that matured over time had always been available. Yet neither can we deny or diminish the delay with which both society and the Church came to denounce the scourge of slavery."

"This constitutes a wound in Christian memory, one from which we cannot consider ourselves detached," he said.