- Martin Kaymer records opening round of 65 at U.S. Open
- German sits three shots clear on five-under
- 2010 champion Graeme McDowell equal second on two-under
- Compatriot Rory McIlroy, the 2011 winner, shoots 71 to finish on one over for the day
Former world No. 1 Martin Kaymer produced a scintillating opening round at the 114th U.S. Open Thursday.
The German carded a five-under-par 65 to move into a three-shot lead in the golf season's second major tournament.
Kaymer, who last month won the Players Championship last month -- known as the "fifth major" -- holed six birdies on a successful day on Pinehurst's second course.
The 29-year-old, who won the U.S. PGA Championship in August 2010, carded the lowest score in a U.S. Open at Pinehurst -- one shot lower than Peter Hedblom's 66 in 2005.
"When you win the Players it's pretty much as if you have won a major, the way the field is," Kaymer told reporters.
"I needed a win, whether it was the Players or a PGA Tour event for my confidence, to feel it's worth it for all the hard work I have put in over the last couple of years.
"That was a nice, huge win and, coming into the U.S. Open and the next few weeks with big events, it's nice if you've just won before. I'm very happy.
"I was asked before what score I would take at the end of the week and I said eight over, so hopefully that's not going to happen now."
Kaymer, who held the No. 1 ranking for eight weeks in 2011, said the course played easier than it had in practice earlier this week.
"They must have put more water on the greens last night," he said.
"I watched some golf this morning and thought it was more playable and even in the afternoon we could stop the ball on the greens.
"It's an exceptional score and very nice to lead the tournament, but I was very surprised the course played fairly soft."
Northern Ireland's Graeme McDowell sits joint-second alongside America's Kevin Na and Zimbabwe's Brendon de Jonge.
McDowell, who won the tournament in 2010, was encouraged with his performance and took advantage
"I spent the last few days just preparing myself mentally for the challenge,knowing that this golf course wasn't going to give much and it was only going to take," he told reporters.
"I really felt like I got my head in the right place the last few days. It wasn't my best ball-striking display this morning, but you don't have to strike it amazing around here, you just have to position the ball correctly at all times, and with a tiny bit more moisture this morning we got lucky.
"In practice yesterday the golf course seemed to be very firm, kind of a weekend set up. I guess the USGA were really relying on some rain last night, which didn't come.
"I'm assuming they put some water on this place this morning and we were able to take advantage of that a little bit early on, and actually think about getting at some of those flags."
Elsewhere, six-time runner-up Phil Mickelson finished the day five shots off the lead after carding a round of 70, with 2011 winner Rory McIlroy on one-over 71.
England's defending champion Justin Rose was way off the pace on two-over, with Australia's Adam Scott a shot further back.
Masters champion Bubba Watson had a nightmare round of 76, which left the American tied for 123rd.