At least 20 stray cats were killed in June, according to a report in Corriere del Mezzogiorno.
Animal rights campaigners said tests proved the meatballs were not only poisoned but also stuffed with nails.
The cats were being cared for by residents of an apartment block on Via Stamen (Stamen road).
“It’s true that stray cats can be irritating, especially in the heat and if they’re dirty, but this act is inexcusable,” Terry Marangelli, the local representative of the Animal Protection (Protezione Animale) charity told the newspaper.
A campaign is now underway to catch the killer. The bounty will be split between Animal Protection and the Animal Liberation Front.