The Cameroon international - signed on a £47.2m deal from Inter Milan this summer as a replacement for David De Gea - made a calamitous error after Leroy Sane's shot somehow wriggled under his body for Bayern's opener.

The Germans went on to win the Group A opener 4-3, although there was a late fightback from the visitors. However, the damage had largely already been done, and Onana admitted that his start to life at Man Utd has not gone to plan.

He told TNT Sport: "It's difficult to lose this way as we started very good but after my mistake we lost control of the game.

"It's a difficult situation for us, and me, as I let the team down. The team was really good but it was because of me we didn't win this game.

• Bayern Munich 4-3 Man Utd - Match report
• Champions League fixtures | Results | Tables
• Get Sky Sports | Stream the biggest moments on NOW

"I'm happy for the work of the team but we have to move on - that is the life of a goalkeeper. We didn't win today because of me.

"Their first shot on target, I made a mistake, so the team went down because of that mistake. I have to learn, be strong and move on although it's not an easy situation. I'm happy with the comeback of the team, we were fighting until the end.

"I have a lot to prove. My start in Manchester has not been good or how I want. The way I played today was one of my worst games.

"It's difficult as we are a big club who wants to win everything. It was a good opportunity to bounce back after the situation we are facing - it's a tough time, we have to be together and continue to work hard."

Onana also made headlines in his Premier League debut, when Wolves were not awarded a late penalty after the goalkeeper's foul on Sasa Kalajdzic. He also let a lob from 45 yards beat him in a pre-season friendly against Lens.

Despite his goalkeeper owning up to his error, Man Utd manager Erik ten Hag insisted on collective responsibility, with his team defensively poor this season.

United have conceded 14 goals in all competitions this season, the most of any Premier League side and have conceded 3 or more goals in three consecutive games in all competitions for the first time since December 1978 under Dave Sexton.

Ten Hag said: "It's good he's doing that [owning the mistake] but it's about the team. Mistakes can be made but you need to bounce back as a team.

"When you score three goals and one player makes a mistake, it's gone. We have to believe we can bounce back, tonight we showed it. You have to stay in the game and keep going despite mistakes.

"For the first 25 minutes, we were better than Munich. Then, that goal was so easy. It's not only Andre, if you see how easy Sane is coming through and that ahs to do with determination. You don't let players so easily through. That's the point we have to cross the line as undefeatable and as a team to win games because it started there."

Ten Hag disappointed with manner of conceded goals

Reflecting on the game overall, Ten Hag was disappointed at how easily Bayern were able to take shots, which increased dramatically after their opening goal.

Man Utd had been the better side in the opening 25 minutes but did not take advantage, while the Germans were naturally efficient in scoring their chances - their two first half goals were their only two shots on target.

He told TNT Sport: "I'm disappointed as we should have stayed in the game. When you score three goals at Bayern you should at least take a point.

"We are in a period where a lot is going against us but we have to make our own luck. When you don't stick the rules or principles of our game you concede goals but we have played three great teams in the last three games.

"Every game is important. Every game is huge. No-one can help you. If you see the first 25 minutes, you have to score but if not, stay in the game and don't allow the opponents to score a goal like we did.

"It's not only about that mistake as even before that it was too easy for the player to have a shot. You have to be consistent in such moments then you will win games."

Kane excited by Bayern team

Harry Kane scored his first Champions League goal for Bayern on Wednesday, scoring from the penalty spot after handball was given by VAR against Christian Eriksen.

He also assisted Sane's opener, continuing his fine start to life in Germany, and says the future with this team is exciting.

"It's always great to score but there's a room for improvement," Kane told TNT Sport.

"As a striker I know I'm going to get chances, it's exciting to play with them [creative players] but we're still getting to know each other. It's exciting what is to come, if we're doing what we're doing now and add the understanding, then it's really exciting.

"When there is a big price tag there is always expectation and you want to repay the club for the faith. It's been a really good start. We're one of the favourites but first of all we need to get the job done in the group and then hopefully look forward to the knockout games.

"They [Man Utd] are going through a difficult spell and suffering with injuries. They have a lot of talent, they can score and turn games around really quickly. I'm not too worried about them, I'm focused on myself. I'm sure they'll improve and get back to their best but I'm just concentrating on us and I'm enjoying it so far."

Bayern manager Thomas Tuchel was also pleased with Kane's European debut for the club, adding: "We played him in a different role in a half position today to turn and to assist to our speed on the sides.

"We found him more involved in the second half, like most of the team. He was more fluid, we found him better in the half spaces, they opened up minute-by-minute.

"Then he had some chances that he took, which is fair enough as a No9. He scored a very important penalty to have a two goal lead again after just conceding so everything is fine."