Inter Milan came from two goals down to earn a famous 4-2 victory over A.C Milan in a gripping Derby della Madonnina that sent the Nerazzurri top of Serie A.
Zlatan Ibrahimovic returned to haunt his former club with a goal and an assist for Ante Rebic as Milan raced ahead before half-time, but the 38-year-old striker could not maintain his unbeaten run since returning to San Siro in January.
The Rossoneri's hopes of causing an upset faded in the space of two second-half minutes that saw Marcelo Brozovic and Matias Vecino plunder quickfire goals to get Inter back on level terms.
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Antonio Conte's men took the lead 20 minutes from time through Stefan de Vrij's superbly executed header and Romelu Lukaku scored in second-half stoppage time to make sure his side leapfrogged Lazio and Juventus into top spot.
Inter looked vulnerable at the back throughout the first half and in the 40th minute Ibrahimovic headed a high ball down for Rebic, who had the simple task of tapping it home from two yards.
On the stroke of half-time Franck Kessie diverted Samu Castillejo's corner to the far post where Ibrahimovic applied a header with just enough power to beat Daniele Padelli and double Milan's advantage.
Brozovic fired Inter back into contention when he sent a brilliant volley into the bottom-left corner past Gianluigi Donnarumma.
Two minutes later it was all square when Alexis Sanchez cut the ball back box to Vecino, whose low drive hit Simon Kjaer on its way into the net.
The game swung from end-to-end before De Vrij peeled away from Alessio Romagnoli and stooped to meet Antonio Candreva's corner with a header that rose over Donnarumma into the top-left corner.
Substitute Christian Eriksen shook the frame of the goal with a stunning 30-yard free-kick before Ibrahimovic dramatically hit the post at the other end, but Lukaku put the game beyond doubt when he rose above Kjaer to convert Victor Moses' cross at the death.
What does it mean? Bianconeri made to pay
After Juventus suffered a surprise defeat to Hellas Verona on Saturday, Inter had a rare opportunity to punish the champion and it recovered from a calamitous first half to do just that.
A meeting with Lazio next weekend will be another serious test of its Scudetto credentials.
Vecino instrumental for Inter
Vecino's positivity was vital in turning a potential upset on its head and he ignited its comeback in a fine all-round performance.
A night to forget for Romagnoli
Milan's defence has been much improved in recent weeks but frailties reappeared in the second half, not least when Romagnoli lost De Vrij as the Inter centre-back scored.
Inter faces Napoli in the first leg of its Coppa Italia semifinal on Wednesday, with Milan taking on Juventus in the other last-four clash 24 hours later.