Bafetimbi Gomis scored a fortuitous winner as Swansea City completed their first ever league double over Manchester United with a 2-1 home victory in the Premier League on Saturday.

Having won 2-1 at Old Trafford on the opening day of the season, Swansea recovered from a goal down to repeat the dose at the Liberty Stadium.

Gomis, who came into the game with only two Premier League goals to his name, was trying to get out of the way when Jonjo Shelvey took aim from 25 yards in the 73rd minute.

But the French striker did not duck quickly enough and the ball took a feint touch off him that sent it flying over the desperate lunge of United goalkeeper David de Gea.

The strike condemned Louis van Gaal's United to their first defeat in 20 matches in all competitions, enabling Arsenal to leapfrog them into third place with a 2-1 win at Crystal Palace.

Swansea came within a whisker of taking the lead inside a minute when Gomis met Gylfi Sigurdsson's corner, only to see his crisp header cleared off the line by Ander Herrera.

Nine minutes later, Gomis popped up unmarked again, but headed over the bar.

United offered precious little in the early stages, despite an equal amount of possession, with Robin van Persie off-target from Angel di Maria's whipped 15th-minute free-kick.

Swansea looked the more purposeful of the sides, with Gomis proving a genuine thorn in United's side.

His reverse pass to Neil Taylor helped to set up Wayne Routledge, but the midfielder's shot was straight at De Gea.

United's first shot on goal came after 20 minutes. Di Maria's cross picked out Rooney at the near post, but the striker's tame strike, from a difficult angle, was comfortably collected by Lukasz Fabianski.

In fact, Fabianski was largely untroubled until Herrera finished off a slick move to put the visitors ahead in the 28th minute.

Luke Shaw's break, Rooney's touch and Di Maria's assist enabled Herrera to beat Fabianski at his far post and claim his fifth goal in a United shirt.

But Swansea were level inside two minutes. Taylor and Shelvey combined on the left and when the ball was teased into the penalty area, Ki Sung-yueng nipped in to beat De Gea with a smart finish.

Van Gaal introduced Antonia Valencia for Paddy McNair at the beginning of the second half. Within 90 seconds of the restart Phil Jones found himself in the referee's notebook for dragging back Routledge on halfway.

United looked suspect at the back and when Shelvey crossed for Ki, the South Korean once again found himself unmarked in the six-yard box. This time, De Gea did just enough to avert the danger.

Van Gaal replaced Shaw with Ashley Young on the hour and United began to look far more decisive in the final third.

When the ball was worked into the box, after another piece of patient build-up, Van Persie hit the side-netting from eight yards.

United have been chastised of late for supposed 'long-ball' tactics, but their approach here was neat, tidy and increasingly menacing.

Young twice applied the pressure with crosses from the left before Marcos Rojo headed over from six yards.

It was all hands to the pump for Swansea, whose goal was leading a charmed life.

But out of nothing, and with manager Garry Monk poised to bring on Jefferson Montero, Shelvey and Gomis combined to win the game.

United lost possession and when Shelvey was afforded time and space in which to compose himself, he grasped the opportunity by unleashing a thunderbolt from outside the box.

The telling touch, however, came from Gomis, who was credited with the goal after Shelvey's celebrations had subsided.