Italy’s far-right interior minister, Matteo Salvini, is suing the country’s celebrated anti-mafia author Roberto Saviano for defamation over a tweet that described him as “minister of the underworld”.

“I filed a lawsuit against Saviano, as promised,” Salvini, who is also deputy prime minister and leader of the League party, wrote on Twitter. “I accept any criticisms, but I do not allow anyone to say that I help the mafia.”

Saviano, a staunch critic of Salvini, posted the tweet in June. He targeted Salvini this week in another tweet showing the bodies of a woman and child floating in the Mediterranean and asking “how much pleasure” the interior minister derived from seeing the image. “The hatred you have sown will overthrow you,” wrote Saviano.