Pope Francis has warned priests and nuns about the dangers of watching pornography online, saying it "weakens the priestly heart".

The Pope, 86, was responding to a question about how digital and social media should be best used, at a session in the Vatican.

Pornography, he said, was "a vice that so many people have... even priests and nuns".

"The devil enters from there," the Pope told priests and seminarians.

As to how to navigate social media and the digital world, he said that they should be used but told them not to waste too much time on it.

"The pure heart, the one that Jesus receives every day, cannot receive this pornographic information," he said.

He advised the group to "delete this from your phone, so you will not have temptation in hand".

Church teaching sees pornography as an offence against chastity.