AC Milan missed the chance to reclaim top spot in Serie A after Andrea Esposito headed in deep into injury time to give promoted Lecce a 1-1 home draw on Sunday.
Champions Inter had taken over as leaders following a 1-0 win over Udinese earlier and they are now a point ahead of their city rivals, who thought they were going back to the summit after Ronaldinho's strike 11 minutes from time.
Milan, who had won seven of their last eight league games, had huge spells of pressure in the late game and should have ended up as comfortable winners with Marco Borriello and Kaka missing glorious chances.
Napoli, on the same points as Milan, earlier beat Sampdoria 2-0 while Lazio are fourth after defeating Siena 3-0 at home thanks to a brace by Tommaso Rocchi and Mauro Zarate's goal. Alessandro Del Piero celebrated his 34th birthday by scoring a third free kick in a week to help Juventus to a 2-0 win at lowly Chievo which puts them joint-fifth with Udinese.
Genoa in seventh are just four points behind Milan in an extremely tight top half after Diego Milito's hat-trick sealed a 4-0 home victory over bottom side Reggina. Fiorentina are also on 20 points following a 2-1 triumph over Atalanta.
STUBBORN DEFENCE
Inter substitute Julio Cruz, who came off the bench to head the equaliser in Inter's 3-3 Champions League draw at Anorthosis Famagusta in midweek, repeated the trick in stoppage time against a stubborn Udinese defence.
Jose Mourinho's side had drawn two of their last three league games 0-0 and they were heading for a third as they continually lumped crosses into the box and lacked creativity.
"Udinese for me are a good team. From a defensive point of view, Inter have played really well," Mourinho told Sky before angrily clashing with an interviewer who criticised him.
Cruz stole the limelight late on but the day still belonged to Del Piero, who curled in another stunning free kick for Juve against coach Domenico Di Carlo's new club Chievo.
Evergreen Del Piero converted a free kick in last weekend's win over AS Roma and scored another in the 2-0 win at Real Madrid in the Champions League on Wednesday, earning a standing ovation at the Bernabeu having also netted a superb first.
An ovation followed his substitution in Verona on Sunday too and Juve coach Claudio Ranieri, who also saw Vincenzo Iaquinta score, hailed the club's greatest ever goalscorer.
"At the moment, Alex is magic. Alex is the captain but not only the captain, he is a leader," he said.