U.S. Open champion So Yeon Ryu shot an 11-under 61 on Friday to take a four-stroke lead after two rounds of the Australian Ladies Masters.

Ryu, who had 12 birdies and a bogey at Royal Pines, had a two-round total of 17-under 127 after an opening 66.

The South Korean's score would have tied the course record held by seven-time Masters champion Karrie Webb, but it will not go in the books due to the lift, clean and place rule in effect on the fairways because of the wet course due to recent rain.

Before Friday, Ryu marked her balls with "62" to represent her career-low round. Now she will be remarking them.

"Finally I can change the number," Ryu said. "The last shot I was really, really nervous, but I made it, so now I'm really looking forward to the last two rounds."

Christel Boeljon finished birdie-birdie-eagle to shoot a 65, putting her in second place. The Dutchwoman's three on the par-5 18th came on a 50-foot putt.

"It's a great feeling, great way to end my round," Boeljon said.

First-round leader Lee Bo-mee (69) and Nikki Campbell (67) were tied for third, seven strokes behind Ryu. Diana Luna and Amelia Lewis each shot a 64 for fifth place along with Felicity Johnson (68), eight strokes behind.

Earlier on Friday, three players were disqualified for unknowingly breaching rules on the preferred lies.

A rules official from the co-sanctioning Ladies European Tour said Corie Hou, Inhong Lim and amateur Annie Choi were disqualified after playing one hole of their second round.

The players, who were in the same group, said they had misinterpreted a local ruling during their first round which allowed preferred lies on fairways but not in the rough.

Choi had an opening-round 2-under 70, five strokes behind first-round leader Lee. Lim shot 80 and Hou had an 81.

The 16-year-old Choi said they had misunderstood what the starter said before they teed off.

"I'm devastated but I accept it," said Choi, who said the group had been told the preferred lies were in place "everywhere" and took that to include the rough.

The threesome had played only one hole of their second round when the rule breach was reported to Ladies European Tour operations director Cyprien Comoy.

All three admitted to taking preferred lies off the fairways in the first round and were disqualified because it meant they had signed incorrect scorecards.

"It was a surprise to them, certainly," Comoy said. "The girls accepted the decision. It is not a pleasant thing but a harsh lesson learned. We accept it was a genuine mistake."