Three bogeys from this group on the fourth hole, just showing how Shinnecock can show its teeth at any moment, even for the world number one as Scottie Scheffler misses the fairway off the tee then misses the green to the right - which leaves him bang in trouble.

JJ Spaun sprays one left off the tee and has to hack it out, while Mason Howell hits the fairway then comes up just short of the green, but it's a pretty difficult scramble to make and he can't get down in two.

Tough hole!

Rory McIlroy finds the fairway at 15 and knocks his second to 15 feet to set up a birdie opportunity. Oooh, it just burns the left edge but that's a stress-free par.

Tommy Fleetwood missed the fairway and green and slips to his second bogey of the day.

Ludvig Aberg, however, pours one in in from 30 feet and joins Sam Burns at two under with his second birdie in three holes.

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Two consecutive birdies for Brooks Koepka puts him smack bang in the thick of things at the top of the leaderboard.

This time he finds a fairway, and as we've been saying all day his iron play has been stellar this year - as he shows by sticking one to eight feet from 170 yards out on the sixth.

And since he's now found out how to putt properly that's not an issue at all as he rolls it in for a three.

Watch out for Chris Gotterup though as he's matched Koepka shot-for-shot on the last two holes for two birdies of his own to improve to level par.

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After that birdie-birdie start, Graeme McDowell is starting to struggle. He visits the tall rough and a bunker on his way to an untidy bogey six at the par-five 16th.

He grimaces as he moves back to level par.

A nice positive move from Tyrrell Hatton at his sixth hole (the 15th) as he punches in from seven feet.

Leader Sam Burns makes another solid par save, this time from six-and-a-half feet to retain his one-shot advantage.

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Two-time champion Brooks Koepka continues his putting improvement as he rolls in a 16 footer for a birdie on the par-five fifth hole.

Again it was a wayward drive but he laid up and then let his approach game, which has been elite all season, do the work with a lovely shot to knock his ball within range.

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Here's JJ.

Very bold. Not sure I could pull this off.

Thumbs up if you'd look good in all-white.

Three pars to start the day for Scottie Scheffler, but he's having to work hard for them on the greens. He's matched by Mason Howell as well in what's an impressive start by the youngster.

Champion JJ Spaun is looking resplendent dressed head to toe in bright white (albeit a little like a caddie at the Masters) but his scorecard isn't anywhere near as clean as he's made two bogeys in three holes.

Rory McIlroy has pummelled a 382-yard drive down the 14th, leaving him a downwind wedge, but his spin control is way off and his ball zips away from the flag and down towards the front of the green.

He's left with a 36-footer and he's a tad aggressive, racing it five feet past, but he drains the one coming back to avoid a second straight bogey.

Ludvig Aberg found the bunker short of the green but displays excellent touch out of the sand and rolls in his par putt, while Tommy Fleetwood gets up and down from over the green to stay level par.

Three good pars it must be said.

Keep an eye on Kristoffer Reitan.

In May, he became the second Norwegian after Viktor Hovland to win on the PGA Tour, when he closed out superbly at Quail Hollow.

He's in the mix early here, burying a 32-foot birdie at the 15th (his sixth) to move to -1.

Graeme McDowell has a 20-footer for birdie at the 15th to move back to two under, but it comes up a little shy and he settles for par.

On he goes to the beastly 620-yard par-five 16th.

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Up at the 14th, leader Sam Burns is putting from 30 feet for birdie.

He's given it a look but has held it a touch low and actually it runs five feet past.

No bother for one of the best putters on tour as he rolls in for par.

Same result for Tyrrell Hatton.

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It's actually a good bogey for Brooks Koepka at four, as he's in the fescue off the tee, has to hack it out with his second then sticks his third in the greenside bunker.

He almost holes out from the sand for a miraculous par, but after those three bad shots he'll happily take a six-inch putt for bogey.

Still can't believe Brooks Koepka of all people has come dressed as a stick of seaside rock for the US Open...

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The wind blows Rory McIlroy's cap off his head as he sends his tee shot down the 13th. The gust also nudges his ball left and it settles down in the rough.

Ball above his feet for the second, he catches a flyer from 128 yards and it hurtles over the green. Chipping back up the hill, his ball skips past the hole to eight feet and he misses the putt. Bogey.

Tommy Fleetwood, from the right rough, also goes long, but he gets up and down to save his four.

Ludvig Aberg, from position A+ in the fairway, sends a towering wedge towards the flag and nearly spins it back into the cup. Easy birdie for the Swede.

Brilliant par for Graeme McDowell.

One of the shorter hitters out there, he finds the knee-height rough at the 523-yard par four 14th, but uses all his strength to advance his ball to the front of the green and chips up to four feet to avoid back-to-back bogeys.

Hanging tough.

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Keegan Bradley experienced Ryder Cup heartbreak just around the corner from Shinnecock Hills at Bethpage Black last year, but he's made a decent start here in the US Open.

The former US PGA Championship winner picks up a birdie at the third to go to one under for his round so far. Bradley arguably should've played in that USA Ryder Cup side as he was bang in form, and there's no reason why he couldn't make a challenge this week with his game and his experience.

That's a beauty from Tyrrell Hatton at the par-four 13th as he measures his approach out of the rough to inside eight feet.

Chance to erase that bogey from his opening hole. Oh he's missed it - frustrating.

Sam Burns shows him how to do it from similar distance, and joins Rory McIlroy at the top.