Carlos Tevez was in sublime form as he scored a hat-trick and also set a goal up for Federico Peluso in the Turin giants' eighth successive league victory - a run in which they have not conceded a goal.
It was another statement of intent for Antonio Conte's side, who showed a positive response to being knocked out of the UEFA Champions League with a defeat at Galatasaray on Wednesday.
Napoli's Champions League campaign also ended in midweek and they took their frustration out on Inter in a thrilling clash at Stadio San Paolo.
Walter Mazzarri endured a miserable first return to Naples since leaving to take over at Inter in May, as Rafael Benitez secured victory against his former employers.
There were five goals in a frantic first half, as Gonzalo Higuain put Napoli in front with his 12th goal of the season only for Esteban Cambiasso to level.
However, Dries Mertens and Blerim Dzemaili scored in the space of two minutes to give Napoli breathing room before Yuto Nagatomo gave Inter hope at 3-2 just before the break.
Ricky Alvarez was sent off in the second half and Jose Callejon sealed the points before Inter goalkeeper Samir Handovic produced a fine reflex save to keep out Goran Pandev's penalty, as Napoli cut the gap to second-placed Roma to two points.
Fiorentina are five points behind Napoli in fourth place after they coasted to a 3-0 home win over struggling Bologna.
Josip Ilicic, Borja Valero and Giuseppe Rossi were on target as Vincenzo Montella's side got back on track following defeat at Roma last weekend.
Livorno were unable to climb out of the relegation zone as Lazio striker Miroslav Klose's first-half double consigned them to a 2-0 defeat in Rome.
Sampdoria moved four points clear of the relegation zone, Eder scoring in a 1-0 victory over Chievo that saw them move above their opponents.
Torino are in seventh after second-half goals from Alexander Farnerud and Ciro Immobile gave them an impressive 2-0 win at Udinese.
Elsewhere on Sunday, Parma were held to a goalless draw at home to Cagliari, while Genoa and Atalanta drew 1-1.
