Okafor punished United's sloppy defending with a brace in the first-half before Lisandro Martinez was sent off after pulling Dominic Calvert-Lewin's hair after the interval.

Casemiro got one back for United, but Leeds held on for their first win against United since a shock 2010 FA Cup success when they were in the third tier.

The Yorkshire club were able to celebrate their first top-flight win against United since 2002 and their first league victory at Old Trafford in 45 years.

A first win in seven league matches lifted Daniel Farke's side six points clear of the relegation zone, with six games left to preserve their top-flight status after last season's promotion.

As well as battling for survival, Leeds are through to the FA Cup semi-finals, where they face Chelsea at Wembley on April 26.

While Manchester City and Liverpool are United's main rivals, their fans' enmity with Leeds supporters goes back decades, featuring numerous clashes between hooligan gangs.

That made the defeat a bitter pill to swallow for United fans, who booed Michael Carrick's side at full-time.

It was only Carrick's second defeat in 11 games since he replaced the sacked Ruben Amorim as interim boss in January.

United remain in third place, seven points ahead of sixth-placed Chelsea in the race to qualify for the Champions League via a top-five finish.

The last time United played Leeds, Carrick was on holiday with former Old Trafford team-mate Wayne Rooney and their respective families in Barbados.

Carrick has revitalised United since taking charge, but one win from their last four games is a step back.

United's trip to Chelsea on Saturday offers another chance to take a step towards returning to Europe's elite club competition for the first time since 2023-24.

Leeds had failed to score in their previous four league games, but they blew United away with a blistering start.

When Jayden Bogle whipped a fifth-minute cross towards Dominic Calvert-Lewin, United defender Leny Yoro was unable to clear and Okafor pounced with a clinical finish from 10 yards.

With Harry Maguire suspended, United were shambolic at the back in the first-half and Okafor netted again after more defensive miscues in the 29th minute.

United made a hash of clearing twice in quick succession and the ball was eventually worked to Okafor, whose strike took a hefty deflection off Yoro as it flashed past Senne Lammens.

Carrick's men were back in action for the first time in 24 days and they looked rusty after the enforced break.

Lisandro Martinez was forced to make a last-ditch tackle on the goal-line to stop Ao Tanka scoring a third for Leeds after the Japan midfielder danced around Lammens.

Benjamin Sesko's effort was cleared off the line soon after the interval and United's nightmare evening continued when Martinez saw red in the 56th minute.

Martinez needlessly tugged Calvert-Lewin's long hair and referee Paul Tierney sent him off after consulting the pitch-side monitor.

Despite their numerical disadvantage, United reduced the deficit in the 69th minute when Casemiro met Bruno Fernandes' cross with a thumping header past Karl Darlow from six yards.

It was Fernandes' 17th league assist this season, closing the gap on the single-season record of 20 held by Thierry Henry and Kevin De Bruyne.

Calvert-Lewin squandered a golden opportunity to wrap up the points, heading straight at Lammens from close-range.

Darlow made a superb save from Sesko's header before Casemiro and Manuel Ugarte had efforts cleared off the line as Leeds held firm in a frantic finale.