Manchester United kept the pressure on leaders Arsenal with victory over Southampton at St Mary's.

First-half goals from Ruud van Nistelrooy and Ryan Giggs gave United what proved an unassailable lead despite Saints' valiant efforts.

Southampton were denied a penalty before the break and with that decision went their chance of getting back into the game.

United have now leapfrogged Newcastle to move into second place, six points behind the Gunners but with a game in hand.

Key moments

14 mins: Van Nistelrooy fires Man Utd into the lead 22 mins: Giggs doubles the visitors' lead 33 mins: Southampton denied a penalty Match pictures

The only down side to a good afternoon's work for United was an injury to Fabien Barthez, who was stretchered off midway through the first half.

Surprisingly, Sir Alex Ferguson dropped the in-form Paul Scholes to the bench and played Ole Gunnar Solskjaer alongside Van Nistelrooy.

However, the change to United's attack did not detract from their ability to find the back of the net.

The game started brightly, with both teams playing good, open football.

I said we had to get our away form right and we have started to do that now Sir Alex Ferguson

Gordon Strachan, who has forged a positive and efficient Premiership unit, had clearly instructed his charges to push forward from the outset.

And they did, with Fabrice Fernandes and Michael Svensson both having chances to give Saints the early initiative.

Michael Svensson's miss from six yards out proved a turning point as United set off on a blistering counter-attack.

"I was pleased with the first half - it went according to plan apart from the two goals. Gordon Strachan

A four-man move culminated in a thumping left-foot half-volley by Van Nistelrooy.

Mikael Silvestre hit a 60-yard diagonal ball to David Beckham, whose flick released Gary Neville and he provided the telling cross for the Dutchman to dispatch the opener.

Such is Southampton's current tenacity, they refused to be overawed and attempted to draw level.

Barthez was stretchered off in the first half

Jo Tessem, who proved a handful for the United defence, thought he had restored parity when, having got in front of Rio Ferdinand, lobbed Barthez only to see the ball drift just over the crossbar.

United responded in kind, again breaking at speed, with Ole Gunnar Solskjaer finding Giggs in the Southampton area.

The Welsh winger, who scored twice against West Ham in the FA Cup at the weekend, scuffed his initial shot but latched onto a fortuitous rebound and fired in United's second.

Despite the two-goal deficit, Southampton continued to press and should have been awarded a penalty when Roy Keane brought down Tessem.

But Lady Luck was clearly not looking down on Saints and Anders Svensson's vehement protestations earned him a booking.

The second half failed to live up to the excitement of the first, with clear-cut chances few and far between.

James Beattie, reportedly a future United target, was largely a peripheral figure, contained by the visitors' defence which saw Silvestre revert to centre-half after the interval.

United now travel to Birmingham on Tuesday in the knowledge that they can cut the gap at the top of the Premiership to just three points.

Southampton: Niemi (Jones 86), Telfer, Lundekvam, Michael Svensson, Benali, Fernandes, Oakley, Anders Svensson, Marsden, Beattie, Tessem (Davies 70).
Subs Not Used: Williams, Arias, Ormerod.

Booked: Anders Svensson, Benali.

Man Utd: Barthez (Carroll 37), Gary Neville, O'Shea, Ferdinand, Silvestre, Beckham (Scholes 69), Veron, Keane, Giggs, van Nistelrooy (Forlan 88), Solskjaer.
Subs Not Used: Phil Neville, Brown.

Attendance: 32,085

Referee: P Dowd (Staffordshire).