Udinese held the leadership outright for a few hours following their 2-0 defeat of Bologna but they were joined once again by Juventus, who beat AC Milan 2-0 in the late kick-off.
Juve's bid to register a third win from five league games appeared to be floundering with the scoreline blank after 85 minutes but midfielder Claudio Marchisio popped up with a late brace to sink the struggling Rossoneri.
In between the goals, Milan had Kevin-Prince Boateng sent off after he collected a second yellow card for clipping Giorgio Chiellini in the face with his arm.
Udinese had a more straightforward victory.
Medhi Benatia opened the scoring in the 29th minute and Antonio Di Natale added a second from the penalty spot 18 minutes from time.
Palermo and Cagliari joined Napoli - 3-0 winners at Inter Milan last night - on 10 points, one adrift of top spot.
Giulio Migliaccio`s first goal of the season and an injury-time Abel Hernandez penalty helped Palermo continue their impressive home form with a 2-0 win over Siena.
Long-serving midfielder Migliaccio set Palermo on their way, opening the scoring in the 19th minute, and, despite Devis Mangia's side being reduced to 10 men in the 55th minute when Federico Balzaretti was sent off, the hosts kept hold of their lead before Hernandez sealed the triumph from the spot late on.
Palermo are unbeaten at the Stadio Renza Barbara since May 22.
Two first-half goals allowed Cagliari to somehow snatch victory over Lecce at Via del Mare.
Thiago Ribeiro put the visitors ahead 10 minutes in and, after Lecce went close to an equaliser on several occasions, Davide Biondini made it 2-0 before the interval.
The hosts continued to press for the remainder of the game but were unable to find a way past goalkeeper Michael Agazzi.
Miroslav Klose grabbed a late winner to hand Lazio an impressive 2-1 victory at Fiorentina.
Fiorentina took an eighth-minute lead through Alessio Cerci but Hernanes equalised before the half-hour mark and although Fiorentina looked the most likely to snatch all three points, it was Germany international Klose who headed in the winner with seven minutes remaining.
Cesena picked up their first point of the season at home against Chievo but should have claimed a victory.
The hosts went into the contest at the Dino Manuzzi stadium with nothing to show for their efforts from the first four games of the season but could have taken the lead when they were awarded a penalty in the second half.
However, Adrian Mutu saw his effort saved by Chievo goalkeeper Stefano Sorrentino as the contest finished goalless.
Sebastian Giovinco inspired Parma to only their second win of the season to lift them out of the relegation zone.
The Italy international scored two and created the third against an off-colour Genoa, who slumped to their second straight defeat.
Giovinco scored his first in the 29th minute before adding a second from the penalty spot in the 42nd minute. He then turned provider for the third goal, scored by captain Stefano Morrone in the 50th minute.
Rodrigo Palacio scored a consolation for Genoa with the final kick of the game from the penalty spot.
Alejandro Gomez's stoppage-time equaliser earned Catania a dramatic 3-3 draw against Novara at the Stadio Silvio Piola.
The hosts twice came from behind to get back on level terms, Marcio Rigoni's penalty cancelling out Nicola Legrottaglie's 14th-minute opener and Takayuki Morimoto equalising again after Francesco Lodi had restored Catania's advantage.
Promoted Novara then went in front for the first time in the 85th minute through substitute Jeda, only for Gomez to snatch a draw for the visitors in the first minute of added time.
Napoli moved to the top of Serie A with a convincing win at Inter Milan, ending Claudio Ranieri's winning start to life as manager of the Nerazzurri .
Walter Mazzarri's side laid out their title credentials in style with a 3-0 success at the San Siro.
A red card for Joel Obi and a dubious penalty decision in the 43rd minute helped Napoli on their way - although Marek Hamsik missed the penalty, Hugo Campagnaro converted the rebound.
Further goals from Christian Maggio and Hamsik in the second half earned Napoli all three points to take them two points clear at the top and leave Inter just one point above the bottom three.
In Saturday's other game, Roma won their second game in a row, beating Atalanta 3-1 at the Stadio Olimpico to end the Bergamo side's unbeaten start to the campaign.
Bojan Krkic opened his account for the Giallorossi in the 20th minute before Pablo Osvaldo added a second after half an hour.
German Denis opened the game up with a goal in the 48th minute, but Fabio Simplicio settled Roma's nerves with the winner nine minutes from the end as Roma moved up to fourth.