Mohamed Salah scored a hat-trick as Manchester United were ripped apart by relentless rivals Liverpool to leave Ole Gunnar Solskjaer under the most intense scrutiny of his near three years in charge.

The 202nd meeting of two of English football’s biggest rivals will live long in the memory after Jurgen Klopp’s men ran amok and recorded the club’s biggest ever win at Old Trafford.

Liverpool were as impressive as United were poor, with scintillating Salah’s treble complementing early goals from Naby Keita and Diogo Jota in a 5-0 rout in which substitute Paul Pogba was sent off.

Sir Alex Ferguson was seen shaking his head in disbelief after the fifth goal, with the visiting fans chanting Solskjaer’s name during an embarrassing display that will test the Old Trafford hierarchy’s support of their manager.

Never before in Premier League history had United gone into half-time four goals behind, but their consistently poor defence was punished by Liverpool as Keita and Jota scored before two Salah strikes.

A cacophony of boos met the half-time whistle and the Egyptian magician completed his hat-trick five minutes after the restart, with Pogba’s red card for a poor tackle on Keita compounding matters.

Liverpool were unable to add anymore and Cristiano Ronaldo saw a goal ruled out for offside in a second half that ended with empty seats and jeers, 10 years and a day since the 6-1 home loss to Manchester City.

There was a crackling atmosphere before kick-off at Old Trafford, where play started at breakneck speed as Bruno Fernandes flashed over at the end of a promising early move for the hosts.

But United’s threat going forwards comes with an unsteady foundation that Liverpool exposed within five minutes.

Hapless Harry Maguire and Victor Lindelof were caught out of position, with Luke Shaw too late to step up in an attempt to play Salah offside. The Egyptian played through Keita to fire home in front of a stunned Stretford End, whose nightmare had just begun.

Roberto Firmino was denied by David De Gea and Salah struck wide as United wobbled, with Liverpool grabbing a second in the 13th minute after Marcus Rashford had fired narrowly wide at the other end.

A mix-up between Maguire and Shaw allowed Keita to play wide for Trent Alexander-Arnold to fizz in a low cross for Jota to turn home at the far post as United paid for more terrible defending.

The home faithful groaned as their side continued to creak at the back, albeit they were still having chances at the other end and Shaw sent an effort skipping just wide.

Curtis Jones replaced the injured James Milner midway through the first half as play swung from end to end, with Alisson Becker denying Mason Greenwood before Keita narrowly missed Firmino at the far post.

The open pattern of play continued as Salah and Rashford traded efforts, before Klopp’s side put their foot on the hosts’ throat.

Liverpool built up smartly and reacted quickest when Salah’s shot was blocked, with the forward bursting towards goal as United’s cumbersome defence watched Keita cross for him to fire home.

Frustrated Ronaldo was perhaps fortunate to avoid a red card for swinging wildly at the ball as Jones lay on the deck, but there was still time for United to unravel further.

Maguire was pulled out of position and the defence panicked, allowing Salah to strike at the far post in the fifth minute of first-half stoppage time.

The United fans roundly booed the team off at half-time, when some supporters made a beeline for the exit. They may have made the right decision.

Half-time introduction Pogba was dispossessed five minutes after the restart and Jordan Henderson played a fine ball with the outside of his foot through for Salah to direct past De Gea and complete his hat-trick.

The hosts thought they had clawed one back when Ronaldo beat Alisson, only for the goal to be ruled out for offside after a VAR review.

Stuart Attwell was the man at Stockley Park and soon advised referee Anthony Taylor to check the monitor having booked Pogba for a late challenge on Keita. Upon review, the card was upgraded to red.

Liverpool fans chanted “Ole’s at the wheel” and “Ole must stay”, with Alexander-Arnold a stunning De Gea save away from adding another goal as United continued to toil.

Andrew Robertson deflected a close-range Edinson Cavani effort onto his own bar as United looked for a consolation as those that remained continued to back their team. Liverpool fans continued to celebrated long after full time.