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United was forced to see off a late surge from the Seagulls as Mbeumo settled matters with one of the final touches of the game.

Matheus Cunha scored his first United goal 24 minutes in, bending his effort around Jan Paul van Hecke before Casemiro added a second 10 minutes later thanks to a wicked deflection off Yasin Ayari.

Benjamin Sesko and Bruno Fernandes, making his 300th United appearance, then saw chances go begging before Mbeumo put the hosts 3-0 up in the 61st minute.

But with Ruben Amorim's team seemingly heading towards a routine victory, former United forward Danny Welbeck dragged Brighton back into it with a stunning free-kick, moments after Mbeumo had an effort saved on to the post. 

Charalampos Kostoulas headed in their second in the second minute of stoppage-time, yet Mbeumo had the final say when he rifled into the roof of the net in the 96th minute, sealing United's fourth consecutive home win.

"I think we played a great game," Mbeumo said after the win. "We are a bit disappointed to concede two goals, but the most important is the win, and in the end, we did it.

"The atmosphere is crazy here. The fans are unbelievable, and it's always good to score goals and especially here.

"I enjoy it a lot here. It hasn't been easy at the start. It's a new environment, a new expectation, but I think with the automatism, with the link-up with the team, I think everything is going the right way.

"The work we put in, the effort, the togetherness we give on the pitch is key, and after we try to stick to the plan, and we try to play as best as possible.

"I like the challenges, came here to a big club, and we want to fight for the best places."

United impressed in the final third, managing 13 shots, nine on target, and Amorim was impressed.

"We played well and suffered in the end. A little bit our fault," the United boss said.

"They did everything. They ran. They played with the ball. They kicked the ball when it was needed. Good game.

"It [Brighton's late fightback] is something that happens in football. They have a lot of talent and quality on the ball.

"They used that momentum to control the game, but we are improving how we respond to bad moments; we did it again."

Brighton had looked out of sorts before Welbeck's free-kick, and early errors ultimately cost it despite the late fightback.

"In the end, it is about execution, and our execution wasn't right," boss Fabian Hurzeler said.

"We made too many easy mistakes, and we have to start in training, take every pass and every touch seriously. We have to improve.

"The character was good, the personality was there, and the belief was there. We never gave up.

"I felt it all the time that there was something. We are consistently there. We worked hard, we had chances, and they had chances, but the main thing was, after our too-easy mistakes, it cost us energy. That energy, we missed it a little bit in the end."