Pope Francis believes journalism based on gossip or rumours is a form of "terrorism", and media that stereotype entire populations or foment fear of migrants are acting destructively.
Francis, who made his comments in an address to leaders of Italy's national journalists' guild, said reporters had to go the extra mile to seek the truth, particularly in an age of round-the-clock news coverage.
Spreading rumours is an example of "terrorism, of how you can kill a person with your tongue", he said.
"This is even more true for journalists because their voice can reach everyone and this is a very powerful weapon."
In Italy, a number of newspapers are highly politicised and are regularly used to discredit those with differing political views, sometimes reporting unsubstantiated rumours about their private lives.
In 2009 several media outlets owned by the family of then-prime minister Silvio Berlusconi came under fire from the journalists' guild over stories questioning the trustworthiness of a magistrate who had ruled against a company owned by the Berlusconi family.
The stories were filled with insinuations about the way he dressed, including the colour of his socks, and the way he took walks in the park.
Francis, who has often strongly defended the rights of refugees and migrants, said journalism should not be used as a "weapon of destruction against persons and even entire peoples".
"Neither should it foment fear before events like forced migration from war or from hunger," he added.