Lautaro Martinez scored all four goals as Inter Milan thrashed Salernitana 4-0 on Saturday to stay top in Serie A, while AC Milan kept pace with their city rivals after overcoming Lazio.
Inter rebounded from their first loss of the season midweek against Sassuolo thanks to a sensational second-half display from Martinez.
The Argentina striker dinked Marcus Thuram's superb ball over home goalkeeper Guillermo Ochoa to break the deadlock just past the hour.
Salernitana's Mateusz Legowski had a goal disallowed for offside before Martinez drilled in his second from a cross from Nicolo Barella.
Martinez completed his hat-trick on 85 minutes after from the penalty spot Thuram was bundled to the ground. He added another with a first-time finish from Carlos Augusto's pass.
Inter are level on 18 points with Milan, who had briefly gone top earlier in the day after they overcame a struggling Lazio 2-0.
Christian Pulisic gave Milan the lead on the hour at the San Siro when he slammed in a bobbling pass from Rafael Leao for his third goal since joining from Chelsea.
Leao was again involved as Milan made sure of the points in the 88th minute, the Portugal winger bursting into the area before cutting the ball back for Noah Okafor to slide home.
"I thought we put a lot of pressure on, it was just a matter of time, we finally opened it up and from there it was a really strong performance," Pulisic told DAZN.
"I haven't been here a long time, there are a lot of new players, but we are really starting to gel well. I am really enjoying my time with the team."
France goalkeeper Mike Maignan returned for Milan after missing the past two games with a thigh injury he sustained in a goalless draw against Newcastle in the Champions League.
Lazio suffered their fourth defeat of the season and dropped to 14th place, with just seven points from as many matches.
- Osimhen on target -
Napoli secured their second victory in four days as Victor Osimhen came off the bench and scored in a 4-0 win at Lecce, bumping the Italian champions up to third.
After a run of three games without a win, Rudi Garcia's side have rediscovered some form heading into next week's Champions League clash at home to Real Madrid.
Centre-back Leo Ostigard headed Napoli ahead early on with his first league goal for the club, but it wasn't until the half-time introduction of Osimhen that the visitors took control of the game.
The Nigerian nodded in a cross from Khvicha Kvaratskhelia on 51 minutes before late goals from Gianluca Gaetano and Matteo Politano sealed the rout.
Politano struck from the spot as Osimhen left penalty duties to a team-mate for the second game running after the club posted a video online mocking him for a missed attempt.
After the player's agent threatened legal action this week, Napoli said they never meant to offend Osimhen.
Napoli remain four points adrift of Inter and Milan.
"It was a well-managed match from start to finish, we wanted to hit hard and score in the first 15 minutes," said Garcia.
"I'm happy for Ostigard who is really a player who's constantly thinking about the team."
"We drew lessons from what happened in Genoa (a 2-2 draw on September 16), it's something that really pleases me," added Garcia.
"All our players are getting back to their best level, that's why the team is now finding this consistency."
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