Ireland's Shane Lowry acknowledges the crowd as he walks onto the 18th green during the third round of the British Open Golf Championships at Royal Portrush in Northern Ireland on Saturday. Photo: Peter Morrison/AP

LONDON  Irishman Shane Lowry stayed a shot clear of the field two thirds of the way through an absorbing third round of the Open Championship on Saturday as the big guns came to the fore in perfect conditions.

Lowry was 13-under-par through 12 holes of round three, 5-under-par for the day, one shot better than Englishman Tommy Fleetwood, who had played a hole more, and two ahead of JB Holmes, who shared the overnight lead with Lowry.

Justin Rose picked up four birdies on the back nine to be 10-under, Lee Westwood was 9-under and Brooks Koepka and Rickie Fowler 8-under-par.

With no wind, players made the most of the benign conditions and on what's generally known as moving day, the big names made their move.

But none more so than Lowry, who birdied three, five and nine to turn in 3-under-par and added two more, at 10 and 12 to reach 13-under-par.

Some of the cheers were reminiscent of the Ryder Cup and Lowry revelled in the atmosphere as he kept his nose in front.

Fleetwood joined him at the top on 12-under at one stage, but two big hits took Lowry to the green at the par-five 12th and two good putts gave him another birdie.

Englishman Fleetwood, like Lowry chasing his first major, was 5-under-par for the day through 13 holes.

Holmes kept his cool while others were going crazy around him, birdieing the second and third, and adding a third at the 12th to stay just two off the pace.

Rose was quiet on the front nine with just one birdie but an eagle at the 12th sparked him into life and birdies at 10 and 12 took him to 10-under.

The 46-year-old Westwood, who has finished in the top three in each of the four majors but has still to win one, hit the front early on but dropped a shot to be 9-under-par through 13.

Fowler put himself in contention with a fine 5-under-par 66 to be 8-under.

"I'm going to have to go out and attack tomorrow," he said. "I've put myself in a position to give it a go."

Defending champion Francesco Molinari, who made the halfway cut right on the mark, carded a 1-over-par 72 to be 2-over-par for the tournament, 12 off the pace.

"Obviously I would have liked to have a better defence of my title, but at the same time you realize that you don't have the trophy but your name is still going to be on it," Molinari told reporters.

"So, bittersweet for now, that's all I can think."

DPA