Defending champion Brooks Koepka leads the US PGA Championship after round one.

The American fired a seven under par round of 63 at the Bethpage Black course in New York.

Koepka leads by one shot from New Zealand's Danny Lee.

England's Tommy Fleetwood is in third place on three under par, one of 16 players that are under par.  Those who started well include Dustin Johnson, Jordan Spieth, Phil Mickelson, Jason Day and Rickie Fowler, all of whom lie on 1 under.

It was another highly impressive performance from 29-year-old Koepka, who won the US PGA and US Open last year.

Coming off a second place finish at Augusta, he fired a bogey-free round, which he believes could have been even better. Koepka failed to birdie either of the par 5 holes.

In last year's US PGA at Bellerive, a second round 63 was the foundation for Koepka's victory. He's happy with the way he is striking the ball and he's already shown he has the composure to win three majors.

If he continues to demonstrate this form, it will be very hard for anyone to catch him.

Graeme McDowell heads up the Irish challenge on level par. He picked up three shots and dropped three shots in his opening round at a venue that doesn't naturally suit his game.

Rory McIlroy is two over par, the same mark as Masters champion Tiger Woods.

McIlroy was great tee to green, but he took 10 more putts than Koepka and his only birdie came at the 18th hole.

Woods, playing competitively for the first time since Augusta, had an up and down round.

He carded two double bogeys, three bogeys, an eagle and three birdies.  Being sick on Wednesday didn't aid his cause.

Shane Lowry and Padraig Harrington are both 5 over par.

Lowry made seven bogeys in his 75, a round which included two three-putts.

Harrington took six bogeys at a long, punishing course where it's difficult to retain momentum when mistakes begin to creep in.