A fantastic clash is brought to an end. Barca will wonder how they failed to open up a first leg advantage, but the Gunners must score in Spain to stand a chance of progressing next week.

Sensible play from the visitors as they keep possession deep into stoppage time.

Walcott wastes the ball, crossing staright to Valdes.

Walcott makes another darting run, but his cross is cut out this time. Three additional minutes at the end of this European classic.

Silly foul by Song on Henry. Still time for a winner.

Fabregas comes back on. Heroic stuff from the Gunners skipper.

Looks like Fabregas may have to come off the pitch. He looks to have hurt himself striking in the penalty.

Penalty for Arsenal! Puyol is adjudged to have brought Fabregas.

Arsenal look tired now. They require a goal from somewhere to avoid needing two at Camp Nou.

Can Arsenal grab what would be an undeserved leveller in the last ten minutes?

Arsenal are constantly looking for Walcott here and rightly so. He is causing Maxwell big problems.

Messi breaks clear and fires straight at Almunia.

Fabregas' effort drifts safely over the top. Brings an end to Arsenal dominance.

Arsenal look hungry again. Walcott's cross causes panic, but is eventually cleared.

Walcott in the act as his sliding cross is deflected by Maxwell and Valdes gathers comfortably.

Maxwell is felled in the Gunners area and Sagna is lucky to get away with that one.

Looks like Guardiola's men are happy to play out time now as they have one foot in the last four of the competition.

Cross into the Barcelona area is gathered by Valdes.

Arsenal look down and out here. Barca are threading the ball around in majestic fashion.

Great goal-saving challenge from Song as Maxwell's teasing ball is almost turned in by Ibrahimovic.

Bendtner almost gets lucky as Puyol's clearance hits him, but drops to Valdes and he mops up the danger.

The ball is in Arsenal's penalty area and they struggle to clear their lines.

Xavi heads wide as Barca launch a counter-attack. Fascinating stuff at the Emirates.

What a chance for Bendtner. The Gunners break and Clichy's cross lands on his head, but Valdes is equal to it.

Messi's free-kick strikes the wall and is cleared.

Pedro misses the target. Fine chance as the midfielder's effort drifts wide of the post from the edge of the area.

Barca are playing keep ball now. They look like they could easily retain their crown this term.

Fabregas bombs on and tangles with Pique. Play-on says the referee.

The crowd is flat now. The hosts need a boost from somewhere.

Absolute shocker for the Gunners. The goal was within 30 seconds of the re-start.

Wenger's decision to rush Gallas and Fabregas back into the team looks like a bad call. Barca coach Josep Guardiola will wonder how his team don't hold a lead.

Thankfully, a chance to breathe as an absorbing first period comes to a close. Barca have been the better side by a country mile, but Arsenal have had their moments.

Another fine cross from Nasri is blocked by Puyol again. The diminutive Frenchman is the hosts' chief threat this evening.

Arsenal need the half-time whistle here in order to re-group.

Fine move from Arsenal ends in Nasri's cross being cut out by Carles Puyol.

Gallas is carried off on a stretcher. He looks unlikely to make a return.

Gallas is down now. The Gunners' team selection looks like it isn't paying off with the Frenchman and Fabregas struggling.

Clichy makes a telling break up the left and wins a free-kick in a promising position. Fabregas' lofted ball is poor and 'keeper Victor Valdes makes an easy catch. Disappointing from the skipper.

Bendtner is offside again as Barcelona's defence looks a little shaky failing to clear Nasri's cross.

Messi's strike nestles straight into Almunia's arms.

Song trips Xavi. Another set-piece in a dangerous position.

Bendtner's telling cross is headed tamely wide by Abou Diaby.

Xavi's pass to Maxwell is placed straight into touch. A rare error from the midfield maestro.

Great play between Ibrahimovic and Messi again allows the big Swede to fire on goal, but he drags his shot wide.

Nicklas Bendtner was almost into the action for the first time, but he is caught offside.

Constant Barcelona pressure is halted as Ibrahimovic fouls challenging Sagna.

Gael Clichy may be fortunate there. Messi dances beyond his challenge but goes down. Referee waves play on.

Fabregas is not looking sharp in the centre of the park and it looks like Arshavin is about to be replaced.

Arshavin is limping around after the challenge that brought his yellow card. The last thing Wenger needs.

Samir Nasri's strike on goal is a whisker away from breaking the deadlock. The crowd are in full voice now.

Better from the Gunners. They are getting fired into the challenges now and Barca don't like it. Sagna's cross is headed away as Arsenal create some pressure.

Arsenal break the play up a bit better and they need more of that to unsettle Barcelona.

Alves' cross is headed straight at Almunia. Barcelona are going for the jugular here.

Xavi's free-kick falls to Pedro and his effort inside the penalty area is headed over by Bacary Sagna.

The visitors continue to pour forward. Can Arsenal weather this extended storm? Vermaelen gives away free-kick by the corner flag deep in their own territory.

Awesome from Barca and Almunia! He saves from Xavi from close range.

Almunia saves point-blank effort from Ibrahimovic.

Messi fires over when well-placed. This is like a practice match for the Spanish giants.

Alexandre Song brings down Seydou Keita and a free-kick is awarded in Arsenal's half, but nothing comes of it.

Arenal lose the ball deep in Barcelona's half and Ibrahimovic runs clear of Thomas Vermaelen, but shoots into the side netting.

Arsenal boss Arsene Wenger is cutting a bemused figure on the sidelines in these early stages.

Further Barca pressure. Daniel Alves storms up the right wing, collects the ball and crosses for Ibrahimovic but he shoots over. Wouldn't have counted as he was offside.

Messi weaves through and smashes straight at Almunia. Ominous signs at the Emirates.

Andrey Arshavin's sloppy pass is almost costly, but Arsenal get the ball back to Almunia. They need to get into the game here.

Barcelona are looking up for this from the off. The Gunners' defence could be in for a long night.

What a chance! From the corner Sergio Busquets has an effort saved from Manuel Almunia.

Messi's storming run leads to a chance as Ibrahimovic's cross is knocked behind for a corner. Danger already for the hosts.