Milan - Cristiano Ronaldo struck twice as Juventus beat Parma 2-1 to pull four points clear of Inter Milan at the top of the Serie A table on Sunday.
Inter's title push hit another stumbling block after a 1-1 draw at lowly Lecce while Ante Rebic fired city rivals AC Milan to a last gasp 3-2 win over Udinese.
Ronaldo broke through just before the break, to score in a seventh consecutive league game, and almost set up a second just after for Aaron Ramsey, but the Welsh international rattled the post.
Andreas Cornelius scored with a towering header to get seventh-placed Parma back level ten minutes after the break.
But the visitors hardly had time to celebrate when Ronaldo broke through again after latching onto a Paulo Dybala cross for his 11th goal in seven games to bring his league tally this season to 16.
"It was important that we win tonight," said Ronaldo. "Lazio won, Inter drew so it was important to take advantage.
"Parma pushed forward in the end, we got a little nervous, but we managed to get the result."
The eight-time reigning champions have a four-point cushion on Inter, who have won only two of their last six league games, and are now also under threat from Lazio, who are just two points behind with a game in hand after hammering Sampdoria 5-1 on Saturday.
Antonio Conte's side had looked set to take maximum points from his hometown team, where he started his footballing career in the 1980s, when Alessandro Bastoni headed the away side in front with 18 minutes remaining.
But Marco Mancosu grabbed a precious point for the southerners five minutes after going behind.
"For me there's always great emotion," said Conte of his return to Lecce.
"Coming back to the Stadio Via del Mare means going back 30-35 years.
"I spent my childhood as a ball boy here. There will always be this attachment, but I am a professional and I try to do this job better."
Lecce - just one point above the relegation zone - were coming off a four-match losing streak, but had held Juventus by the same scoreline back in October.
"Congratulations to them, even if conceding this goal leaves a bitter taste in the mouth," added Conte.
Croatian forward Rebic hit a brace, including the stoppage time winner, against Udinese that snatched a dramatic win that gave troubled AC Milan back-to-back league victories and moved them up to eighth, two points from the Europa League spots.
Star striker Zlatan Ibrahimovic got his first start at the San Siro after scoring last weekend at Cagliari.
The 38-year-old Swede did not get to celebrate in front of the home crowd but he has provided a confidence-boost for the seven-time European champions, who have taken seven points in three matches since his return.
"The arrival of Ibrahimovic has given us even more depth and conviction, which has helped us," said coach Stefano Pioli.
Former Liverpool and Chelsea attacker Fabio Borini, who left Milan on Tuesday, scored his first goal on his debut for new club Hellas Verona in a 1-1 draw at Bologna that leaves them a further two points.
In the race for the Champions League, Roma bounced back from back-to-back league defeats with a 3-1 win over struggling Genoa that put them back in the top four, three points in front of fifth-placed Atalanta ahead of their match with SPAL on Monday.
Cengiz Under opened the scoring after just five minutes and the match looked as good as won a minute before the break when a cross from Leonardo Spinazzola - whose move to Inter broke down midweek - bounced in off Genoa's David Biraschi.
Former Lazio striker Goran Pandev quickly pulled a goal back but Edin Dzeko had the last word with 16 minutes to go, pouncing on a error from goalkeeper Mattia Perin to send Genoa below Brescia into penultimate position.
Mario Balotelli came on late for lowly Brescia and was sent off just seven minutes later in a 2-2 draw against sixth-placed Cagliari.
The Italy forward entered the field in the 74th minute, but received a yellow card for a foul on Fabio Pisacane before picking up a second when he turned to argue with the referee.