Gylfi Sigurdsson of Swansea City celebrates scoring his team's second goal during the Barclays Premier League match between Manchester United and Swansea City at Old Trafford on August 16, 2014 © Getty Images

Gylfi Sigurdsson had the first chance of the match when the visitors were awarded a free kick 25 yards out, but his curling effort was held by David de Gea.

Swansea continued to test the hosts, and took the lead with just under half-an-hour gone when the ball fell to Ki Sung-yueng on the edge of the box, allowing the midfielder to drill it into the bottom corner.

Ki Sung-Yeung is congratulated by his Swansea teammates after scoring the opener against Man United on August 16, 2014 © AFP

The hosts showed more urgency before the break, but Swansea's defence held firm to ensure that they led heading into half time.

Louis van Gaal's side were back on level terms early in the second half when Wayne Rooney struck the ball on the volley from the six-yard box.

Wayne Rooney of Manchester United celebrates scoring his team's first goal during the Barclays Premier League match between Manchester United and Swansea City at Old Trafford on August 16, 2014 © Getty Images

The newly-appointed captain came close to adding a second later in the half as he tried his luck from a free kick, striking the ball against the crossbar.

The miss proved costly though as Swansea regained the lead when Sigurdsson fired in from close range after Wayne Routledge scuffed his initial effort.

Bafetimbi Gomis had a chance to score on his Premier League debut for the visitors after coming off the bench, but a last-gasp challenge from Phil Jones denied the Swansea striker.

United's Adnan Janujaz is approached by Swansea midfielder Gylfi Sigurdsson on August 16, 2014 © AFP

Ashley Young had a half chance from 25 yards late on as the hosts desperately looked for a late equaliser, but Lukasz Fabianski was left to make a comfortable save.

United pressed again as Adnan Januzaj tried to get a shot away deep into stoppage time, but his effort was accidentally blocked by Rooney, allowing Swansea to hold on for the win.