Barcelona claimed their 100th Champions League win courtesy of a stoppage-time winner against a Celtic team who emerged with tremendous credit if no reward.

The Scottish side stunned Camp Nou by taking the lead, the seventh time already this season that Barcelona have lost the first goal in a match. Later, Celtic were to suffer the cruelty of defeat when only seconds remained.

The La Liga club recovered from their early setback as Jordi Alba stole in at the back post to secure victory. Barcelona merited that on the balance of play, but they should still afford Celtic quiet respect. "It is a sore one to take, I thought the team was magnificent," said the Parkhead manager, Neil Lennon.

"It is bittersweet; it's hard to take losing in the manner we did but I am so proud of the players. I think we have given the club and the country a huge shot in the arm. We can take a lot from the game. I think we have won a lot more admirers. I am very proud of them tonight, even though I don't like losing.

"I said to the players before the game there probably wasn't a person outside of the dressing room who thought we could get anything, aside from us [the coaching staff] because we know them so well. They are talented young players and people are starting to sit up and take notice of them now, which is fantastic for us. The most important thing is the reputation of the club and we will leave here with that firmly intact."

Entering last night's match, Barcelona had won 14 and lost none of their previous 17 home games in the competition. They also remain unbeaten in La Liga this season, but the concession of 10 goals in their last six outings apparently constitutes cause for local concern.

There should have been little surprise attached to the fact Celtic spent the opening exchanges toiling to get out of their own half. Alexis Sánchez, preferred in the home attack to David Villa, should have opened the scoring within two minutes but he screwed the ball wide from a Lionel Messi pass.

Marc Bartra was the next to threaten, with a header which Fraser Forster sharply batted away. From the subsequent break, however, Celtic created ripples across the European football scene by opening the scoring.

A foul on Scott Brown during the visitors' counterattack allowed Charlie Mulgrew to curl a menacing free-kick into the Barcelona penalty area. Georgios Samaras was afforded sufficient space to angle a header goalwards; the ball also took a crucial deflection off the shoulder of Javier Mascherano. Víctor Valdés therefore found his first touch of the ball was to remove it from his net.

Celtic suffered a double blow in the first half's dying moments. The influential Samaras limped off with a twisted ankle, moments before Andrés Iniesta played a wonderful one-two with Xavi Hernández and supplied a low finish. Suddenly the tenacity shown by Celtic when not in possession had been clinically undone.

Barcelona's vulnerability at cross balls was highlighted again eight minutes after the restart. From a Mulgrew corner, Efe Ambrose headed wide with the Celtic defender's team-mate, Victor Wanyama, better positioned.

Messi was denied by a fine save from Forster as Celtic endured a spell on the ropes. The goalkeeper, part of the England party for recent matches against San Marino and Poland, further endorsed that status with a one-handed stop from a Messi header.

Just as Lennon's men looked like holding firm – Villa had struck a post – Alba intervened. Adriano's cross eluded the entire Celtic defence, allowing his fellow full-back to score from all of two yards.

"The top teams go right to the end," Lennon added. "We have done that ourselves a lot in Scotland. The longer the game went on, the longer Barcelona pressed us into our half. We weathered more or less everything – it was just one last attack where things didn't go for us.

"You have to look at our three games, the team has performed very well in all of those games so far. We always felt it was a three-way fight for second place."