Manchester: Manchester United displayed their killer instinct as the champions moved two points clear at the top of the Premier League with a 3-1 win over title rivals Chelsea at Old Trafford on Sunday.

Sir Alex Ferguson's side scored three times before half-time through Chris Smalling, Nani and Wayne Rooney, while Chelsea squandered a host of chances as the visitors crashed to their first defeat under new boss Andre Villas-Boas.

Fernando Torres pulled one back for the visitors in the second half, with Rooney also missing from the penalty spot, but United's fifth win in five matches ensured they took advantage of second placed Manchester City's 2-2 draw at Fulham.

Smalling opened the scoring with his first Premier League goal in the eighth minute before Nani doubled the lead from long range.

Rooney added a third just before half time, his ninth in five Premier League outings this season.

Torres reduced the deficit with his second goal in 19 Premier League appearances, but the Spaniard also produced an early candidate for miss of the season -- stabbing wide of an open goal in the closing stages.

United equalled a club record of 18 straight home league wins, while former Porto coach Villas-Boas lost a league match for the first time since April 2010.

Chelsea had enjoyed the better start, with David de Gea forced into a save from a Ramires volley after just two minutes.

Daniel Sturridge also shot wide from just outside the area as the visitors continued to threaten but United took the lead with their first real attack.

Ashley Young sent over a free kick from the left and, with Chelsea appealing for offside, Smalling got in behind the defence to head past Petr Cech.

Torres was quickly given the chance to equalise for Chelsea after latching on to a slack Anderson pass, but the Spaniard's low effort missed the target.

Frank Lampard had an effort deflected past the post by Jonny Evans and from the Juan Mata corner that followed, Branislav Ivanovic headed straight at De Gea.

Chelsea should have pulled level when Mata played Torres through and the Spaniard squared for Ramires, who shot weakly at De Gea from less than 10 yards out.

The visitors continued to dominate possession and chances and from a Torres flick from Ashley Cole's cross, Sturridge was once again denied by De Gea.

But eight minutes before half time United doubled their lead with a fine effort from Nani.

Evans picked out the Portuguese on the right with a long cross-field ball and the winger cut inside Mata before finding the top corner with a powerful shot from long-range.

And United made the game safe just before half time thanks to Phil Jones' long run from half way.

The former Blackburn defender broke into the area and passed for Nani before Terry's attempted clearance hit Nani and fell for Rooney, who touched in at the far post.

Torres ended his goal drought just 30 seconds after the restart to give Chelsea some hope.

The Spaniard raced through on to a pass from half-time substitute Nicolas Anelka to score with a chipped finish.

But 10 minutes later Nani drove a shot on to the bar and collected the rebound before he was pulled down by Jose Bosingwa in the area, with referee Phil Dowd awarding a penalty.

However, Rooney slipped as he ran up to take the penalty and shot well wide of Cech's goal.

Chelsea continued to press forward, with substitute Romelu Lukaku having an effort deflected wide from close range before Torres was denied by De Gea.

Rooney was also denied by the post after stabbing Patrice Evra's cross towards the corner.

With seven minutes remaining, Ramires played Torres through but the striker went around De Gea and shot embarrassingly wide of an open goal from close range.