Carlos Tevez's fifth goal in a week after just three minutes seemed to set the Red Devils up for a comfortable win over Aalborg - and what would have been only the holders' third in Europe this term.

But an unexpected first-half response from the visitors left United trailing at the interval.

Although Wayne Rooney levelled, the hosts could not find a winner - knowing they will be in Japan on Club World Cup duty on Friday week when a last-16 draw is made that could pair them with, among others, Real Madrid and Inter Milan.

At Celtic Park, the hosts went ahead after 14 minutes when Villarreal goalkeeper Sebastian Viera let Mark Wilson's cross to slip through his grasp to allow Shaun Maloney to nod home.

Aiden McGeady doubled the hosts' advantage in stoppage time at the end of the first half, 10 minutes after Guille Franco had been sent off for Villarreal for elbowing Gary Caldwell.

A below-par Arsenal slumped to a 2-0 defeat to leave itself with a tougher path towards Champions League glory.

With his side already qualified for the last 16 and with several key men - like captain Cesc Fabregas and striker Robin van Persie - carrying injuries, manager Arsene Wenger felt confident enough to take a calculated gamble with his team selection against a well-organised Portuguese outfit, who had never lost at home to an English side in a European tie.

However, the move back-fired as the much-changed Gunners never really got going and were undone by goals either side of the break by Bruno Alves and Lisandro Lopez.

Arsenal will now be drawn against one of the group winners next Friday - which include Juventus, Bayern Munich and Barcelona - and must play the second leg away from home.

In the other match in Group G, Ukrainian side Dynamo Kiev made sure of its place in the UEFA Cup courtesy of a 1-0 victory over Turkish outfit Fenerbahce, Roman Eremenko grabbing the game's only goal after 20 minutes.

Juande Ramos marked his first game in charge of Real Madrid with a convincing victory at the Bernabeu but it was not enough for Real Madrid to finish top of Group H.

Raul grabbed a brilliant brace as the Ramos era began with a 3-0 win over Zenit St Petersburg, but it was Italian giants Juventus who progressed as group winners courtesy of a goalless draw against BATE Borisov.

Madrid and Juve progressed to the last 16 level on 12 points, although Claudio Ranieri's side could have made it through in more convincing fashion had Sebastian Giovinco not missed a 53rd-minute penalty.

Bayern Munich ensured they progressed as winners of Group F after a 3-2 win at Lyon.

The German champions raced into a 3-0 lead inside the first half but a spirited fightback by Lyon after the break made for a thrilling encounter.

Elsewhere in Group F, Fiorentina sealed their place in the UEFA Cup as Alberto Gilardino's 66th-minute strike secured a 1-0 win over Steaua Bucharest, who had Pawel Golanski sent off 18 minutes from time.

Champions League results
Celtic 2 Villarreal 0
Manchester United 2 AaB 2
Steaua Bucuresti 0 Fiorentina 1
Lyon 2 Bayern Munich 3
FC Porto 2 Arsenal 0
Dynamo Kiev 1 Fenerbahce 0
Juventus 0 BATE Borisov 0
Real Madrid 3 Zenit St Petersburg 0