Saviano, who has lived under armed guard since publishing his mafia best-seller Gomorra in 2006, has repeatedly criticised Salvini for his anti-immigration policies and lashed out last month over a threat by the interior minister to lift his police protection.

"I filed a lawsuit against Saviano, as promised. I accept any criticisms, but I do not allow anyone to say that I help the mafia," Salvini wrote on Twitter, also referring to his anger at claims he celebrated the death of a child.

Earlier this week Saviano posted a picture on Twitter of a dead woman and child floating in the Mediterranean and questioned "how much pleasure" the minister from the anti-immigration League party took from the image.

"The hatred you have sown will overthrow you," wrote Saviano.

The 38-year-old writer has previously denounced the "foul" atmosphere in Italy since the new populist government took office on May 31, warning that anyone could be targeted in an interview with the Corriere Della Sera newspaper.

On Thursday, Saviano responded to Salvini's announcement of legal action by accusing the minister of being "afraid of critical voices".

"Salvini in court will be called to tell the truth," he said.