By Phil McNulty Chief football writer at the Emirates Stadium
Nasri scored once in each half
Samir Nasri struck twice as Arsenal beat Manchester United and delivered an emphatic confirmation of manager Arsene Wenger's belief that they are still serious Premier League contenders.
Nasri's deflected shot opened the scoring in the 22nd minute and he doubled their advantage three minutes after the interval with a powerful finish from Cesc Fabregas's precise pass.
Substitute Rafael volleyed United back into contention with a minute of normal time left - but Arsenal survived six extra minutes and an outbreak of mass anxiety at the Emirates to clinch the three points.
It was a victory they merited, with United creating and wasting chances but never carrying the same sense of self-belief as Arsenal in a highly charged atmosphere.
Wenger proud of Arsenal players
Arsenal have suffered 10 days of soul-searching and criticism after allowing Spurs to secure an unlikely draw and losing in acrimonious circumstances at Stoke City but they responded with an almost open show of defiance on and off the pitch.
They even had the strength of character to cope with losing goalkeeper Manuel Almunia to injury in the closing stages to keep United at bay.
United boss Sir Alex Ferguson will have been frustrated by his side's wastefulness, with Wayne Rooney and Cristiano Ronaldo guilty of throwing away obvious openings, but he can have no serious complaints about the result.
For Arsenal, this performance and result will have only made Wenger - who was given noisy vocal backing throughout the game - even more entrenched in his belief that he will not sacrifice his principles for a more physical style of play.
Arsenal were without injured Emmanuel Adebayor and the suspended Robin van Persie, while United predictably restored Rooney and Dimitar Berbatov after the Champions League draw at Celtic.
But Arsenal looked anything but under-strength in a vibrant first 45 minutes that brought a host of chances at both ends and a deserved lead for Wenger's side.
It was United, however, who had the first opportunity when Arsenal keeper Almunia inexplicably picked up a backpass from Mikael Silvestre inside the first two minutes.
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Arsenal were relieved when Anderson's free-kick was half-cleared and Michael Carrick turned the loose ball wide.
Wenger appeared to have instructed Arsenal to probe United's right-flank, where Gary Neville looked desperately uncomfortable at the start of what was a harrowing afternoon for the England defender.
Gael Clichy's cross was headed off target by Nicklas Bendtner, who then failed to get on the end of another dangerous ball from Nasri.
Rooney missed an even better chance for United after 17 minutes, carelessly lofting an inviting ball from Ronaldo over the top when it seemed certain he would score.
Arsenal took full advantage of the reprieve to take the lead five minutes later, when Nasri's shot took a crucial deflection off Neville and wrong-footed Edwin van der Sar.
It was a wonderfully open game but Arsenal were playing like a team stung by recent criticism and the sight of old rivals United had only inspired them further.
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Fabregas had a shot deflected just wide but United were threatening themselves and Almunia needed to save well from Ji-Sung Park.
If there was a frustration for Arsenal, it would have been that the crucial second goal had eluded them, despite their dominance.
They did not have to wait long to get it as Nasri doubled their advantage three minutes after the restart.
Fabregas was at the centre of affairs again, punishing United for failing to pick up Nasri when he threaded through a perfect pass for the France midfield man to beat Van der Sar with an emphatic finish.
United, uncharacteristically, were lacking a cutting edge and wasted a perfect opportunity to grasp at a lifeline immediately after Arsenal's goal.
Park found Ronaldo unmarked at the far post but he dragged his shot across the face of goal with only Almunia to beat.
Almunia then required lengthy treatment after an accidental clash with Carrick as United refused to give up on the belief that they could get back into an enthralling encounter.
He carried on but was clearly in discomfort and was replaced by Lukasz Fabianski with 12 minutes left.
United also replaced Rooney with Carlos Tevez and Anderson with Ryan Giggs in what was clearly a last throw of the dice by Ferguson as time ran out.
Rafael, who had replaced Neville in the 63rd minute, pulled one back in the final minute with a spectacular left-foot volley from the edge of the box after Arsenal failed to clear a Giggs cross.
Almunia's injury meant six minutes of injury time but United could not create another chance and Arsenal's fans and players celebrated wildly at the end.
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