Brazilian Jo and Richard Dunne were the first-half goalscorers for City
Swaggering Manchester City turned on the style with a devastating display of attacking football to crush Portsmouth at a buoyant Eastlands.
Jo slotted City into the lead before Richard Dunne bundled in the second.
Influential Stephen Ireland made two superb passes to set up clinical strikes for Robinho and a rejuvenated Shaun Wright-Phillips after half-time.
Substitute Ched Evans finished off a great team move for the fifth before Gelson Fernandes completed the rout.
Both clubs came into the match having won two and lost two of their first four Premier League games - but the task facing Portsmouth appeared greater as City boss Mark Hughes selected the attacking Brazilian trio of Elano, Jo and British transfer record signing Robinho.
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On the day that City announced the date for the formal takeover of the club by the Abu Dhabi United Group - 23 September - the club's new chairman, Khaldoon Al Mubarak, was unveiled to fans just before kick-off.
And he did not have to wait long to be entertained.
Within two minutes £18m Brazilian forward Jo fed £32.5m Robinho who had Pompey keeper David James stretching at full-length to push his wicked curling shot away.
Ten minutes later, the pair linked up again with Robinho cleverly switching the play to pass into the path of the onrushing Wright-Phillips only for the alert James to race out and deflect the little winger's shot with a smart block.
With Wright-Phillips in a rampant mood, City were attacking in vibrant waves despite the busy efforts of Lassana Diarra in protecting the visitor's defence at the base of midfield.
City were running riot and took the lead in the 13th minute when Robinho played a clever pass into space for Jo who, timing his run to perfection against Portsmouth's high back-line, rounded James on the edge of the box and rolled the ball into an empty net.
Striker Peter Crouch should have done better from a header after 20 minutes but Portsmouth were too busy trying to stem the tide to really threaten themselves.
Two minutes later City were two up.
Elano swung in a low corner and, with the near post unprotected, James had to scramble across to save only for Richard Dunne, on his 29th birthday, to scramble the ball home from three yards despite the attentions of Sol Campbell.
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Portsmouth right-back Glen Johnson then put in a low cross from the right and Crouch stepped behind Richard Dunne to fire his shot inches wide of the post, but he should have tested under-worked City keeper Joe Hart.
Ireland was a growing influence in City's midfield and he fed Robinho, who was showing his full array of tricks, for the Brazilian to test James with a snap-shot.
Argentine international Pablo Zabaleta had to clear a Campbell header off the line just before half-time but that was a rare scare for City.
Their imperious swagger continued and 10 minutes after the break they put the game beyond doubt.
New City chairman Khaldoon Al Mubarak (r) waves to the fans
Ireland, a product of City's famed youth academy, lofted a clever ball over static centre-back Distin and Jo muscled his way onto the ball to feed Robinho who clinically curled the ball past James just inside the post from 15 yards.
Ten minutes later City were four up after Ireland slotted a sumptuous low pass through for Wright-Phillips to power a high shot past James' inside post for third goal in his second spell back with the club.
Ched Evans replaced Jo minutes later and was soon on the scoresheet as City's confidence soared.
Elano sent a pass out wide for Robinho to spin onto and the Brazilian attacked the byline to pass into the box for Wright-Phillips.
His audacious back-heel totally flummoxed Pompey's defence and Evans was able to finish with ease from 10 yards.
The rout was completed late on when Javier Garrido's cross from the left was fumbled by James as Wright-Phillips pressured and Fernandes bundled home the loose ball into an empty net.
Man City: Hart, Zabaleta, Richards, Dunne, Garrido, Kompany, Wright-Phillips, Ireland (Gelson 77), Elano, Robinho (Sturridge 85), Jo (Evans 71). Subs Not Used: Schmeichel, Michael Ball, Hamann, Ben-Haim.
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