efe-epaPortrush, Northern Ireland

Ireland's Shane Lowry fired an impressive 8-under 63 in Saturday's third round of the Open Championship to grab a four-shot lead heading into the final day.

Lowry came into the day tied with American J.B. Holmes, but he beat his playing partner by six shots at the Royal Portrush Golf Club in this seaside town to move to 16-under, the lowest 54-hole score in the 159-year history of this major tournament.

The Irishman was 3-under on the front nine even though he settled for par at both of the par-5 holes - two and seven.

He then heated up even more on the back nine, notching birdies on the par-4 10th, 15th and 17th holes, the par-5 12th and the par-3 16th, thrilling a crowd that chanted his name amid a party atmosphere at this links course.

"That's the most incredible day I've ever had on a golf course. I can't describe what it was like. I said walking off the 17th tee that, 'We might never have a day like this again, let's enjoy this last 30 minutes,'" Lowry told reporters afterward.

The 33rd-ranked Irishman, however, said he is prepared for a tougher day of golf on Sunday, when rainy and windy conditions are expected to lead to much higher scores.

"I know it's going to rain, I know it's going to be difficult at times, but I just have to go out there and play my game."

England's Tommy Fleetwood, meanwhile, is in second place at 12-under - two shots ahead of Holmes - after firing a 5-under 66 in the third round.

Fleetwood was on a blistering pace through 12 holes, notching birdies on three par-4 holes (the first, fifth and 10th) and also the first two par 5s of the day.

His momentum slowed the rest of the way, although he did not give any strokes back and heads into Sunday only having made two bogeys the entire tournament.

"I think the last three or four holes it was strange. I'd gone bogey free today, played really well and I had chances on 11, 14 and 17. You can easily get frustrated, but it's hard. You have to look at it realistically," Fleetwood told the media.

American world No. 1 Brooks Koepka and English world No. 4 Justin Rose are tied for fourth after three rounds of play.

Although they find themselves seven shots behind Lowry, tougher weather conditions on Sunday could cause the three players ahead of them to stumble and provide the opening they need. EFE-EPA