Inter maintained their perfect record in Serie A this season with a 1-0 win over Verona on a night when Juventus were held by bottom club Frosinone.
A second-half goal from Felipe Melo proved enough for Inter to triumph at San Siro, with a fifth straight victory seeing them move into a three-point lead at the summit.
Torino had started the evening in second place but were beaten 1-0 away at Chievo, Lucas Nahuel Castro scoring the only goal of the game with 15 minutes remaining.
Fiorentina are now Inter's nearest challengers after they won 2-0 at home against Bologna, Jakub Blaszczykowski and Nikola Kalinic grabbing the goals.
Juventus, meanwhile, find themselves 10 points off top spot after they could only manage a 1-1 draw at home against Frosinone.
Simone Zaza scored his first goal for his new club to break the deadlock, yet Juventus paid the price for failing to capitalise on their dominance when Leonardo Blanchard nodded home an injury-time equaliser for the visitors.
Despite picking up their first point of the season, Frosinone are still stuck at the foot of the table due to Carpi holding Napoli to a 0-0 draw.
Roma suffered their first defeat of the campaign away at Sampdoria, an own goal from Konstantinos Manolas with five minutes to play settling a tight game at Stadio Luigi Ferraris.
Sampdoria had taken the lead through Eder, only for Roma to get back on level terms thanks to on-loan Chelsea winger Mohamed Salah.
Lazio were 2-0 winners over Genoa, who had Issa Cissokho and Goran Pandev sent off in the second half. Filip Djordjevic and Felipe Anderson found the net to help the home side bounce back from their 5-0 loss to Napoli at the weekend.
There was also a red card in Palermo, where the home team saw Luca Rigoni dismissed in their 1-0 defeat to Sassuolo.
Sergio Floccari was on target 10 minutes before the break as Sassuolo secured an away victory that moves them up to third in the table.
