Lautaro Martinez came off the bench to score a dramatic stoppage-time winner as Inter beat Serie A rivals Napoli, who had two players sent off late on.
Earlier on Wednesday, Juventus had scored a late equaliser to draw 2-2 at Atalanta and edge them nine points clear of the Partenopei at the top of the table.
Napoli, though, could not reduce the deficit and saw defender Kalidou Koulibaly dismissed for sarcastically applauding the referee after a late caution, before Inter goalkeeper Samir Handanovic made a superb double save and a follow-up shot was cleared off the line.
Inter then claimed a 1-0 win when Martinez lashed the ball home in added time, with Napoli forward Lorenzo Insigne shown a red card for an off-the-ball incident ahead of the final whistle.
The build up to the match had been dominated by the news Inter had "temporarily suspended" midfielder Radja Nainggolan "for disciplinary reasons". The Belgian reportedly was at loggerheads with Inter head coach Luciano Spalletti.
When the action got under way at the Giuseppe Meazza Stadium, it was almost a perfect start for Inter as from the kick-off captain Mauro Icardi looked to lob Napoli goalkeeper Alex Meret, but the ball rattled the crossbar.
Inter continued to press during the opening stages as Matteo Politano fired over.
Napoli created an opening after 15 minutes following a counter when Arkadiusz Milik set up Insigne, but Handanovic made a smart low save.
The visitors were forced into a change after 25 minutes as captain Marek Hamsik hobbled off with what looked to be a thigh issue. Serbia defender Nikola Maksimovic was sent on as the team regrouped.
After 31 minutes, Ivan Perisic crashed in an angled volley following a corner, but the offside flag was already up.
Inter midfielder Joao Mario headed straight at Meret, before Icardi saw his scrambled effort hacked off the line by Koulibaly.
Early in the second half, midfielder Marcelo Brozovic sent a 20-yard effort over and Kouliably made an important block as Icardi looked set to shoot in the six-yard box.
After 81 minutes, Koulibaly pulled back Politano as they ran down the wing, and was cautioned. The Senegal defender sarcastically applauded referee Paolo Mazzoleni – which resulted in him being shown a second yellow card swiftly followed by a red.
With six minutes left, Meret produced a fine reaction save to deny Icardi's header from a corner.
Inter substitute Balde Keita went down looking for a penalty under a clumsy challenge from defender Raul Albiol.
Napoli then almost snatched victory at the death as substitute Dries Mertens saw his shot palmed out by Handanovic, who then recovered to save Insigne's follow-up effort before Piotr Zielinski's drive was blocked on the line by Kwadwo Asamoah.
In stoppage time, Keita got away down the left. Matias Vecino stepped over the cross, which deflected through for Martinez to dispatch back into the bottom corner, sparking wild celebrations around the San Siro.
As tempers boiled over during the closing moments, Insigne was shown a red card after tussling with Keita in an off-the-ball incident.
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