Betting favourites United won the 151st Manchester derby at a canter as goals by Cristiano Ronaldo and Carlos Tevez helped Sir Alex Ferguson's side move to within four points of retaining the Premier League title.
Meanwhile, Chelsea secured third place in the table with a resounding 4-1 win over Arsenal at the Emirates Stadium.
In the play-offs, a sensational performance by Luke Daniels sent Shrewsbury Town through to the League Two final for the second time in three years as they beat Bury in a penalty shoot-out.
At Wembley later this month the Shrews will play Gillingham who beat Rochdale thanks to a Simeon Jackson brace.
In the SPL, for the second time in three weeks, Inverness Caley Thistle and Hamilton Accies played out a 1-1 draw, despite the visitors playing the final 23 minutes off the match with only ten men.
In rugby league, St Helens powered into the quarter-finals of the Challenge Cup with a 42-8 thrashing of Catalans Dragons at Knowsley Road.
Saints led 18-8 at the interval, but ran out easy winners in the end, scoring eight tries to one - with Francis Meli, Gary Wheeler and Paul Wellens all crossing twice.
Warrington Wolves thrashed Featherstone Rovers 56-8, while Sheffield Eagles pushed Hull KR hard before the Super League outfit won out 34-24 at New Craven Park.
Huddersfield Giants saw off Rochdale Hornets 38-12 at the Galpharm Stadium, with the home side running in seven tries.
Salford City Reds notched 11 tries as they thrashed Batley 66-4, having led 48-0 at the break at Mount Pleasant.
In golf, Argentina's Daniel Vancsik shot a final round 65 to wrap up a six-shot victory at the BMW Italian Open in Turin.
Meanwhile, Jenson Button made it four wins out of five in Formula One this season by powering to victory at the Spanish Grand Prix, with Rubens Barrichello completing a Brawn one-two.
Red Bull enjoyed a fine afternoon with Mark Webber finishing third and Sebastian Vettel coming in fourth, with home favourite Fernando Alonso taking fifth place on the final lap.
Button started from pole position but lost the lead to team-mate Barrichello before turn one, before a crash near the back of the field led to the safety car being deployed.
Barrichello then led the way when the race proper got underway, but Button's switch to a two pit-stop strategy proved to be crucial in a race of few overtaking manoeuvres.
Team-mate Barrichello stuck with his original three-stop plan, but was unable to find the pace needed to match Button in the latter stages of the race.
Felipe Massa gave a promising display in the much-criticised Ferrari, being among the front-runners before being forced to conserve fuel near the end of the race, dropping back to sixth place at the chequered flag.
The top eight was completed by Nick Heidfeld and Nico Rosberg, while reigning world champion Lewis Hamilton could only manage ninth in his McLaren.