Defending champion Yang Yong-eun and American Rickie Fowler fired four-under-par rounds of 67 to set the pace in the first round of the Korea Open on Thursday.

U.S. Open champion Rory McIlroy lurked one shot back after carding a 68 in windy conditions at the Woo Jeong Hills Country Club in Cheonan, alongside Hong Soon-sang and amateur Lee Soo-min.

I started with a birdie which helped a lot, Yang told reporters. I think 12 or 13 under par will win it and I'm sure I can be there or thereabouts.

Yang, the first Asian man to win a major at the 2009 U.S. PGA Championship, overturned a 10-stroke final round deficit last year to win his second Korea Open title.

Fowler, still chasing his first career victory, said: I drove the ball well which is important. I made a few birdies, but I didn't play the par fives as well as I had hoped.

The 22-year-old was two-over for the par-fives.

I hit poor drives on those holes and on this course you have to drive the ball well to score, said last year's PGA Tour Rookie of the Year.

The score would have been really low if I had played them better.

McIlroy squandered his chance to claim at least a share of the first round lead after splashing into water at the 11th for a double-bogey six.

The world number three also over-ambitiously attempted to drive the final green where he dropped his fourth shot of the round, but promised to keep attacking.

I started nicely. I was three under through nine holes, said the Northern Irishman. The shot on 11 was just a bad shot, while on 18 the wind just grabbed it. I was aggressive, but I want to play aggressively.