McIlroy, who opened with a 64 and led from start to finish two years ago, made it five birdies in a row when he hit two superb shots onto the green at the long third and two-putted.

With four to play he remained seven-under, two ahead of Sergio Garcia, whose return to form continued with more birdies at the second and third.

At the other end of the scale, former European Open champion Kenneth Ferrie laboured to the turn in an 11-over 46 and then retired with an ankle injury.

He already led by three from a group which included defending champion Miguel Angel Jimenez, former world number two Sergio Garcia and 2004 Open champion Todd Hamilton.

With a chance to move up from his current seventh place in the world to a career-high fourth, McIlroy had already birdied the 550-yard 13th - his fourth - and short 15th when he rolled in a 14-footer two holes later.

He completed a back-nine 33, four-under, with an eight-foot putt and then started the outward half with two more birdies from 22 and five feet.

Garcia's ninth place finish in Qatar last week was his best for almost a year, but he probably needed to be in the top two this weekend to climb into the game's top 64 and qualify for the WGC-Accenture World Match Play in Arizona later this month.

Westwood, Kaymer and Woods - the world's top three in that order - had been put together as expected and were among the later starters on day one.