Swedish amateur Robert Karlsson shot a 5-under 67 Thursday to share the lead with countryman Alexander Noren and Jaco Van Zyl of South Africa after the first round of the Nordea Masters.
The 22-year-old Karlsson, one of only three amateurs in the tournament, had seven birdies and a double bogey on the 7,603-yard Bro Hof Slott course — the longest on the European Tour this year.
Karlsson said the lead took him by total surprise.
''We had set no goals aside from just having fun,'' Karlsson said of his caddie. ''I hadn't really expected this when I stood by the tee this morning. It feels really good. I started to feel more and more comfortable with the shots and then it just kind of flowed. It felt like I was in the moment the whole time. I wasn't thinking either back or forward.''
Noren made eight birdies, one bogey and a double bogey, while Van Zyl had six birdies and a bogey.
Bubba Watson shot a 71 and Dustin Johnson, who shared second place in the British Open on Sunday, finished with a 73.
The tournament changed its name to Nordea Masters from Scandinavian Nordea Masters this year.