The Nerazzurri boss felt that his side should have been awarded a spot-kick for an apparent foul on Diego Milito by Christian Maggio before the Partenopei's second goal
The Nerazzurri fell behind five minutes into the second half of a spirited Coppa Italia quarter-final clash when Edinson Cavani fired home from 12 yards out, after being upended in the box by Thiago Motta.
Ranieri had no problem with the Uruguayan being awarded the penalty, but he felt that Inter should also have been awarded a spot kick when Diego Milito went down after tangling with Christian Maggio in the area before Cavani sealed victory for the hosts with his injury-time strike.
"There were two penalties," the Nerazzurri boss told Rai Sport. "But I have only seen one [given] - and it decided the game.
"And there was also [what should have been] the sending of Maggio for a foul as last man on Milito."
Ranieri admitted that he had exchanged words with match official Domenico Celi after the match.
"It's true," he confessed. "I went by the referee after the game. I talked to him and I told him my thoughts.
"But it's too bad because we made a good effort, especially in the second half."
Napoli's victory means that they will now face Siena for a place in the Coppa Italia final.