The Belgian match officials who failed to rule out two goals by Dimitar Berbatov and wrongly judged Wayne Rooney to be offside as he scored another against Celtic have admitted they were surprised to find out they had blundered.

Frank De Bleeckere, the match referee, and his assistants, Peter Hermans and Alex Verstraeten, have come under fire for their displays at Old Trafford on Tuesday night.

Berbatov was clearly offside when he scored each of the opening two goals, while Rooney was onside when he claimed another in the match, which United eventually won 3-0.

The officials claimed they were unlucky and insisted the fact that Celtic players did not complain at the time backed up their decisions.

De Bleeckere said: "At the moment itself, we were not aware of the error. There was no protest. I walked off the field with a good feeling. But when you see the images, it's a shame.

"The officials are a team. We did okay at the European Championships and in the Champions League. We must help each other and see it as a learning curve."

Verstraeten and Hermans both failed to flag for offside against Berbatov and were labelled Dopey and Sleepy following Gordon Strachan's pre-match reference to Snow White.

Verstraeten said: "I can deal with such comparisons. We have not yet talked about it as a group.

"I admit to the mistakes, but we also ask for understanding. Offside decisions are the hardest to judge. We are only human flesh and blood.

"This is the first time that we have made a mistake in 52 international matches. It is our bad luck that the mistakes came at goals. It is no consolation that Manchester United would have won without these decisions."

He added: "Some players argue their case in front of us, but no Celtic player protested. That proves that the offside decisions were very tight. At the end of the match, I was surprised when I saw the television images."