Manchester United and Villarreal remain favourites to qualify from Group E despite both being held to draws on Wednesday.
United needed a late header from Ryan Giggs - the Welshman pouncing after Artur Boruc could only parry Cristiano Ronaldo's 25-yard drive - to deny Celtic a crucial win that had looked on the cards after Scott McDonald's sublime lifted finish had given the Bhoys a 13th-minute lead.
Villarreal had to settle for a point after Anders Due's late free-kick earned AaB Aalborg a 2-2 draw under new manager Allan Kuhn.
Giuseppe Rossi had fired Villarreal into the lead on 41 minutes, only for Jeppe Curth to latch onto Caca's backheel pass in the 54th minute to level.
Substitute Guille Franco appeared to hand the Spanish side the win, but Due's late drive denied them.
Olympique Lyon took over top spot in Group F with a comfortable 2-0 win over Steaua Bucharest that maintained their unbeaten record in the group stages.
Juninho curls home a brilliant free-kick to put Lyon ahead against Steaua
Having recovered from two goals down to beat Steaua 5-3 two weeks ago, Lyon secured victory in an altogether more measured fashion thanks to Juninho's brilliant free-kick and a late Anthony Reveillere counter-attacking effort.
They will now qualify for the next round if they draw against Fiorentina next time out.
And so will Bayern Munich if they get anything from their match against Steaua after they ground out a 1-1 draw in Italy on Wednesday.
Adrian Mutu had volleyed Fiorentina into a deserved first-half lead but Tim Borowski earned Bayern a draw after being left unattended in the box and slotted home late in the second half.
Robin van Persie wasted a series of chances but Arsenal stayed top of Group G despite a lacklustre 0-0 stalemate against Fenerbahce that prompted boos from the home crowd.
The Gunners, without a win in three matches, know, however, that a win over Dynamo Kiev or Porto in their remaining group matches will see them into the knockout stages.
FC Porto kept up their hopes of progressing, leapfrogging Kiev into second spot in the group with a last-gasp victory over the Ukrainian side.
Artem Milevskiy drilled Dynamo into a first-half lead, but Rolando equalised with a 10-yard header in the 69th minute and Lucho Gonzalez wrapped up a dramatic victory in injury time when he slotted into an empty net from Pele's right-wing cross.
Juventus's Del Piero celebrates his sublime free-kick at the Bernabeu
Alessandro del Piero grabbed a brace as Juventus secured their qualification from Group H with a clinical 2-0 win over Real Madrid.
The Italian giants soaked up plenty of Real pressure before poaching a goal in either half, Del Piero driving home from 20 yards and then curling home a delightful 25-yard free-kick to reward a fine tactical display from Claudio Ranieri's men.
Zenit St Petersburg kept alive their hopes of reaching the knockout phase with a 2-0 win at BATE Borisov, though they must beat Juventus and Real Madrid in their remaining games to stop the latter joining Juve in the knockout stages.
Pavel Pogrebnyak put Zenit ahead with a neat chipped finish on 34 minutes before French defender Sebastien Puygrenier was sent off for a second yellow card on 73 minutes, reducing Zenit to 10 men.
However, Danny wrapped it up four minutes into injury time, the midfielder skipping past two defenders before drilling low into the corner.
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