Brighton & Hove Albion midfielder Alexis MacAllister fired the winner from the penalty spot deep into stoppage time to snatch a 1-0 win for his side over Manchester United in a pulsating Premier League clash on Thursday.

The spot kick was awarded after referee Andre Mariner consulted the pitchside monitor for a possible handball on Man United defender Luke Shaw, and he pointed right to the spot before MacAllister buried his penalty to hand Brighton a massive win.

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The defeat leaves Erik ten Hag's side in fourth place on 63 points, four ahead of fifth-placed Liverpool and with a game in hand over their Merseyside rivals, while Brighton move up to sixth on 55 points.

The home side dominated possession and could have gone ahead as early as the fourth minute when Japan winger Kaoru Mitoma snapped up a loose pass from Victor Lindelof, but he fired his shot straight into the face of David De Gea.

Ten Hag cut a frustrated figure after the match, telling reporters: "Every defeat is a disappointment, to lose it in the last second is annoying. The first minute sets everything up: We created a good chance, we were not clinical enough.

"In attack, after we gave away a chance, the ball in the head for David. In the end, we also gave away the goal, it's annoying. If you can't win because you don't score, then you can't lose."

Mitoma was a threat throughout, creating several chances for himself before teeing up Danny Welbeck to fire high and wide from the edge of the box early in the second half as United struggled to pass the ball out of defence.

After getting booked in the first half, United midfielder Casemiro was lucky not to pick up his second yellow card as he hacked down MacAllister on the edge of the box in the in the second half.

Tempers flared in the 68th minute as United winger Antony -- angry at not being awarded a free kick -- was penalised for a tackle on MacAllister before getting into a confrontation with Lewis Dunk that earned both players a yellow card.

Brighton continued to press forward looking for a winner, with substitute Solly March and MacAllister both forcing superb saves from De Gea as the clock ticked towards 90 minutes.

United looked set to secure a draw, but there was late drama when Shaw was found to have handled the ball in the box after a VAR review, and MacAllister blasted home the spot kick nine minutes into stoppage time to secure the win.

Ten Hag defended Shaw after the match, despite giving up a needless handball when his hands flew into the air into the path of an incoming corner kick.

"He did well," Ten Hag said of Shaw's all-around performance. "The annoying thing is the free kick before, it was never a free kick. I have seen bad tackles without whistles, every attack you make, they kick you, and then there's a fair block, and then a corner, and then they score.

"The last five games we had four wins, and one draw. We were on a good run and we are improving and in the first half, we should've gone up. We had to stay focused until the end of the game."