Published: Oct 27, 2011 9:43 AM EDT
Updated: Oct 28, 2011 6:30 AM EDT

SHANGHAI (AP) - U.S. Open champion Rory McIlroy shot an 8-under 64 on Thursday to take a one-stroke lead in the Shanghai Masters, the lucrative invitational tournament that isn't sanctioned by any of the major tours.

The 22-year-old star from Northern Ireland had eight birdies - five on the back nine - in his bogey-free round on Lake Malaren's Jack Nicklaus-designed Masters course.

The 30 players are vying for the $2 million first prize, the richest in golf.

American Hunter Mahan was second. He had seven birdies, including three in a row on the back nine, then settled for a par in the 18th hole when his birdie try glanced off the lip of the cup.

England's Paul Casey and Ian Poulter and Ireland's Padraig Harrington were three shots back at 67.