Wayne Rooney hailed Machester United's 2-1 win over Arsenal, after a fine counter-attacking display, as a "massive" result.

A farcical Kieran Gibbs own goal gave United the lead against the run of play and, as the hosts poured forward in search of an equaliser, Rooney took advantage of acres of space at the back to make it two.

Olivier Giroud pulled one back deep into injury time but United sealed their first away win under Louis van Gaal.

"It's a very important victory," Rooney said. "We weathered the storm at times, especially first half. Then we knew we could hit them on the counter-attack, we knew they were vulnerable on the break.

"We rode our luck at times, our goalkeeper (David De Gea) was fantastic. They had possession and we hit them on the break, which was our game plan.

"We hope now we can go on a good run of games and judge the position we're in after Christmas. We've got two home games coming up, we feel we should be taking six points out of them and we want to build a bit of momentum going into the new year. Today was a massive result in terms of starting that."

All the pre-match hype had been over Danny Welbeck facing his former club, but the England forward failed to prove United manager Louis van Gaal wrong for letting him go as the visitors rode their luck.

De Gea saved an early one-on-one from Jack Wilshere, who later went off with an injured ankle. The England midfielder had also been fortunate to avoid a red card after clashing with the much taller Marouane Fellaini and putting his head into his chest, an incident which sparked a brief melee.

After Arsenal had failed to turn their superiority into goals in the first half, they had a clear chance just after the interval but Welbeck could not beat De Gea at the near post after cutting in from the left.

United punished Arsene Wenger's men by sweeping into the lead thanks to some comical defending from Arsenal. American actors Jim Carrey and Jeff Daniels - the stars of "Dumb and Dumber To" - were introduced as guests on the Emirates Stadium pitch before kick-off and might have felt they were watching a rerun from their own movie.

Goalkeeper Szczesny came out to palm away a deep cross from the left, but was clattered into by Gibbs. The loose ball dropped to Antonio Valencia, who drilled his shot wide of the target, only to see it deflect off the grounded Gibbs and into the net.

Szczesny, meanwhile, had taken a heavy blow in the ribs and had to be replaced by Emiliano Martinez.

During the stoppage, there was an incident near the United bench, with substitute Darren Fletcher involved in an angry exchange with Arsenal supporters who were sitting in the rows immediately behind. When play eventually restarted, Alexis Sanchez glanced a diving header straight at De Gea.

Arsenal, though, were made to pay for pressing such a high line as United added a second on the break.

Angel Di Maria skipped away down the right, drawing Nacho Monreal out of position before squaring to Rooney, who ran into the area and clipped the ball over the goalkeeper.

Argentina forward Di Maria could have added a third early in the eight minutes of stoppage time after breaking clear from a corner, but floated the ball wide of the far post.

Giroud then cracked a shot in from 20 yards, but an expected grandstand finale didn't materialise.