Rory McIlroy has a one-stroke lead at Southern Hills ©Getty Images

Rory McIlroy holds the 18-hole lead after a brilliant opening round of five under par at the Professional Golfers' Association of America (PGA) Championship in Oklahoma.

McIlroy, who started on the 10th tee, made four consecutive birdies on holes 12 through 15 to burst into the lead and was rewarded for aggressive play at Southern Hills Country Club.

The four-time major winner - who represented Ireland at the Tokyo 2020 Olympics and plays this event under a Northern Irish flag, moved as low as six under at one point, but two bogeys in the final four holes robbed McIlroy of a dream first round and even bigger lead.

Still, he birdied the ninth - his last hole - and the score of five under gives McIlroy a one-shot lead over the field.

It is McIlroy's best score in the opening round of a major in more than a decade.

Playing partner Tiger Woods, the 15-time major champion once again on the comeback trail, struggled on a course which is not an easy walk and finished four strokes over par.

Fellow American and major champion Jordan Spieth completed the blockbuster group and ended on two over.

Will Zalatoris and Tome Hoge - both American - are one shot behind McIlroy.

Mexico's Abraham Ancer, 2017 winner Justin Thomas and Rio 2016 bronze medallist Matt Kuchar - the latter two both American - are at three under and tied for fourth.

Olympic champion Xander Schauffele, another player from the United States, and in-from Australian Cameron Smith are among those three shots behind McIlroy.

Reigning champion Phil Mickelson is not defending the PGA Championship this year.

Jon Daly, the 1991 winner who like Mickelson is a larger-than-life figure emanating from the US, is playing and at one stage held the lead, but fell back to two strokes over par.