كتب : Hatem Maher
Wayne Rooney opened the scoring after 20 minutes when he latched on to Wes Brown's neat pass and slotted home, to score his first league goal since October.
Rooney turned from scorer to provider ten minutes later after his clever chipped cross was superbly diverted into the net by Louis Saha's right foot.
The in-form Cristiano Ronaldo added the third just before the break after curling a stunning free-kick into the top corner of the net.
Saha completed the rout four minutes from time when he converted a penalty after Nani was brought down by Danny Collins.
Defending champions United are in charge of the table with 45 points, two ahead of second-placed Arsenal, who take on Portsmouth later on Wednesday.