Published: Oct 27, 2011 9:32 AM EDT
Updated: Oct 28, 2011 6:30 AM EDT

SHANGHAI (AP) - Rory McIlroy reeled off five birdies on the back nine to take a one-stroke lead over Hunter Mahan after Thursday's opening round of the Shanghai Masters, a lucrative invitational tournament not sanctioned by any of the major tours.

McIlroy, the 22-year-old U.S. Open winner from Northern Ireland, had eight birdies in total and no bogeys at the just-completed, Jack Nicklaus-designed course at Lake Malaren Golf Club in the outskirts of Shanghai. He finished at 8-under 64.

"If I can play as solid for the next three days as I did today, I feel as if I'll be very difficult to beat," he said.

Mahan had seven birdies, including three in a row on the back nine, but he missed his final chance on the 18th hole when his putt just glanced off the lip of the cup. The 29-year-old American is hoping to make up for a disappointing finish at the Tour Championships last month, where he lost in a sudden-death playoff to Bill Haas.

"You have to go out there and try to make as many birdies as you can. A lot of great players are here so you can't take your foot off the pedal, you've got to be aggressive," Mahan said. "The course is set up well enough so that it's not too long - (there are) good length holes. But it's still challenging in a lot of areas so you have to be cautious on a few shots."

England's Paul Casey and Ian Poulter and three-time major winner Padraig Harrington of Ireland were three shots behind McIlroy at 5-under 67. Anthony Kim of the United States and Li Chao of China were another stroke back at 4-under 68.

Even though the first-year tournament isn't sanctioned by a major tour and is being held the same week as the PGA Tour's Asia Pacific Classic in Malaysia, it still managed to attract an elite, 30-player field by offering a total purse of $5 million and a winner's check of $2 million - the richest first-place prize in golf.

All the top players are also getting appearance money, and last place pays $25,000.

The winners of each of the majors and the Tour Championships this year took home $1.44 million apiece, while the winner of the Asia Pacific Classic will be awarded $1.3 million.

There are 10 major winners in the field, including three from this year: McIlroy, Masters winner Charl Schwartzel of South Africa, who was six strokes back after shooting a 70, and PGA Championship winner Keegan Bradley, who had a 72. Among the other former champions are Retief Goosen of South Africa (69), Y.E. Yang of South Korea (69), Geoff Ogilvy of Australia (73) and Jim Furyk of the United States (75).

Lee Westwood of England also finished with a 69. The world No. 2 didn't look sharp for much of the day, but he nearly had an eagle on a long putt from the fringe of the green on the par-5 13th - the ball stopped less than an inch in front of the hole.

There are no ranking points at stake at the tournament and PGA players did not need a competing-event release in order to take part. The PGA Tour was not pleased about the event, which is being run by the International Management Group, particularly since 16 PGA players are in the field.

But the players themselves are excited about the new event.

"With a small field like we have here, and I think I may get in trouble for saying this, but I'm kind of glad it's not sanctioned by the European or PGA tour," said American player John Daly, who only has six cuts on the PGA Tour this year, but finished the first round in a share of eighth with Westwood, Goosen, Yang and Sweden's Robert Karlsson with a 69.

"It shows that China is doing something on their own. They're saying, 'Hey, we may not need the PGA Tour or European Tour, no disrespect.'"

Mahan said the $2 million payout was only one of the reasons he decided to play in the tournament before competing in the HSBC Champions event, also being held in Shanghai, next week.

"They're building golf courses daily here. This is a place you want to market yourself," he said. "No question this is one of those events I think is going to grow through time and get bigger and bigger and I'm excited to be at the beginning part of it."