Manchester City v Manchester United | Premier League | Match Highlights

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

Ruben Amorim's first Manchester derby looked like ending in a third successive league defeat after Josko Gvardiol's header put City ahead but Ivory Coast youngster Diallo tuned the game on its head in stunning fashion.

Diallo was fouled by City's Matheus Nunes after latching onto a dreadful back pass by the same player with Fernandes stroking home the penalty in the 88th minute.

City had hardly got over that shock when seconds later it became the "Diallo Derby" as he sent the visiting fans into delirium with a superb finish from the tightest of angles.

What was initially a worrying slump in form by champions City has now snowballed into a full-on nightmare before Christmas for Pep Guardiola's side as they have now lost eight of their last 11 games in all competitions, winning one.

They stay fifth in the table with 27 points from 16 games, nine points behind leaders Liverpool having played a game more.

United remain in the bottom half with 22 points but will hope their smash-and-grab raid at The Etihad Stadium will spark a move up the table during the festive period.

Fernandes breathed a sigh of relief after the game, having missed a gilt-edged chance to equalise shortly before Diallo lit the touch-paper for United's stunning win.

"He's been doing well, he's been doing great things, I think there's still a lot to come from him ... When he's like this, he's unstoppable," the Portuguese midfielder said.

City did not even muster a shot on target in the second half as they looked barely recognisable from the side that has won four successive Premier League crowns.

Midfielder Bernardo Silva made no attempt to sugar-coat a gut-wrenching loss.

"We totally deserved what happened," he told Sky Sports. "In minute 87 in a derby and you are winning 1-0 and have a corner and the ball ends up as a penalty for them, if you make these stupid decisions you deserve to pay for that."

Neither side started the game brimming with any fluency after bleak recent results and United did not have a shot on target before the interval.

Amorim flexed his muscles ahead of kick-off, leaving Marcus Rashford and Alejandro Garnacho out of his matchday squad and he was then forced to make an early switch as Mason Mount hobbled off after 14 minutes to be replaced by Kobbie Mainoo.

It took 20 minutes for City to muster a shot at goal as Phil Foden's half-volley went wide while at the other end Diallo struck the post with a shot but was offside anyway.

City's fans were becoming restless but the tension lifted around the stadium in the 36th minute when, from a short corner, De Bruyne's cross was deflected and dropped invitingly for Gvardiol to guide a header past André Onana.

It was the eighth goal United have conceded from a corner this season, a figure only topped by Wolverhampton Wanderers.

Tempers boiled over soon afterwards as City's Kyle Walker and Rasmus Højlund came together like two rutting stags and Walker fell theatrically to the ground, earning both players yellow cards after a melee involving several more.

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 taking the points, especially after Fernandes dinked a golden chance wide after being played through.

But City's world collapsed around them when Nunes's terrible back pass was seized upon by Diallo and Nunes desperately tried to make amends but merely hacked Diallo down.

Fernandes tucked away the penalty but worse was still to come for the hosts as Diallo sprinted through, cleverly dinked the ball around goalkeeper Éderson and then saw his shot dissect two covering defenders before nestling in 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."