Manchester United piled on the misery for struggling Premier League champions Manchester City as late goals from Bruno Fernandes and Amad Diallo snatched an unlikely 2-1 away win from the jaws of defeat on Sunday.

Ruben Amorim's first Manchester derby looked set to end in a third successive league defeat after Josko Gvardiol's header had put City ahead, but Ivory Coast youngster Diallo turned the game on its head in stunning fashion.

Diallo was fouled by City's Matheus Nunes after latching onto a terrible backpass from the same player, and Fernandes slotted home the spot-kick in the 88th minute.

City had barely got over the shock when it became the Diallo Derby seconds later as he sent the home fans into raptures with a superb finish from the tightest of angles.

What began as a worrying slump in form for reigning champions City has turned into a pre-Christmas nightmare for Pep Guardiola's men, who have now lost eight and won just one of their last 11 games in all competitions.

They remain fifth in the table on 27 points from 16 games, nine points behind leaders Liverpool who have played a game more.

United remain bottom of the table on 22 points, but will be hoping that an impressive display at the Etihad can help them move up the table over the festive period.

Neither side started the game with much confidence after recent disappointing results and United failed to register a shot on target before the break.

Amorim flexed his muscles before kick-off, omitting Marcus Rashford and Alejandro Garnacho from his matchday squad, and was then forced to make an early change when Mason Mount limped off after 14 minutes and was replaced by Kobbie Mainoo.

It took 20 minutes for City to get on the scoresheet, Phil Foden's half-volley going wide and Diallo hitting the post for offside at the other end.

The City fans were growing restless, but the tension in the stadium was relieved in the 36th minute when De Bruyne's cross from a short corner was deflected and dropped invitingly for Gvardiol to head past André Onana.

It was the eighth goal United have conceded from a corner this season, a tally second only to Wolverhampton Wanderers.

Tempers boiled over soon after when City's Kyle Walker and Rasmus Højlund collided like two rutting stags, with Walker theatrically falling to the ground and both players receiving yellow cards after a tussle that involved several others.

Højlund later posted on Instagram: "Manchester is red Violets are blue What a brilliant performance But the Oscar goes to..."

City were strangely subdued after the break but still looked like getting the points, especially after Fernandes spurned a golden opportunity after being played through.

But City's world collapsed around them when Nunes' terrible back-pass was latched onto by Diallo and Nunes desperately tried to make amends, only to hack Diallo down.

Fernandes dispatched the spot-kick, but there was worse to come for the home side as Diallo sprinted through, skilfully rounding goalkeeper Éderson before unleashing a shot that flew past two defenders and into the net.

"The second half, we pressed good, we wanted to win, this is the derby ... we showed today we can win every game and we are very happy to win today," said Diallo. "I want to thank God for this. Let's enjoy it for today and focus on the next game."