Pope Francis has a warning for Italy's mobsters - they will go to hell if they do not repent.

The pontiff yesterday delivered his most forceful denunciation yet of organised crime.

The occasion was a prayer vigil at a Roman church for relatives of innocents killed by the Mafia, during which the names of 842 victims were read aloud as a sombre Francis looked on.

After voicing his solidarity with the family members, he said he could not leave the service without speaking to those not present: the "protagonists" of Mafia violence.

Addressing these absentee mafiosi, Francis was unsparing:

"This life that you live now won't give you pleasure. It won't give you joy or happiness," he said.

"Blood-stained money, blood-stained power, you can't bring it with you to your next life. Repent. There's still time to not end up in hell, which is what awaits you if you continue on this path."

Francis has spoken out frequently about the evils of corruption and wrote a short booklet on corruption and sin in 2005 when he was archbishop of Buenos Aires.

But this was his first major address to Italian victims of organised crime, who were gathering near Rome for an annual retreat organized by a Mafia-fighting priest that takes place each March 21, the first day of spring.

The brutality of Italy's mobsters was driven home this week by the death of Domenico Petruzzelli, a two-year-old killed along with his mother and her companion in a mob hit in southern Taranto in which assailants opened fire on their car.

Domenico's two older brothers, sitting in the backseat, escaped unharmed.

Francis mentioned the hit in his remarks, ending his exhortation to mobsters with a reminder.

"You had a father, a mother. Think of them," he said. "Weep a little. And convert yourselves."