Updated

County Cork, Republic of Ireland (SportsNetwork.com) - Finland's Mikko Ilonen fired a 7-under 64 on Thursday and took a 2-stroke lead after the opening round of the Irish Open.

Ilonen is a three-time winner on the European Tour with his last title coming last year at the Nordea Masters.

Robert Karlsson, Marcel Siem and Magnus A. Carlsson share second place as they posted 5-under 66s on the Deerpark Course at Fota Island Resort.

Anders Hansen posted a 4-under 67 on Thursday. He was joined in fifth place by Edoardo Molinari, Daan Huizing and Matthew Baldwin.

Local favorite Graeme McDowell shot 3-under 68. He is tied for ninth place with 12 other players at minus-3. Defending champion Paul Casey opened with a 2-under 69 and he is tied for 22nd.

Rory McIlroy struggled to a 3-over 74, which left him tied for 125th place.

Ilonen opened with four straight pars. He converted back-to-back birdie chances at 14 and 15. After another pair of pars, Ilonen made birdie on the par-5 18th to make the turn at minus-3.

He tripped to a bogey on the first, but fought back with birdies on the third and fourth to move to 4-under.

Ilonen converted a birdie on the sixth and made it two in a row as he also birdied the seventh. He capped his round with a birdie on the ninth, his last.

"It was a slow start really. The first sort of four or five holes I felt like I can't get anything going, but I stayed patient and then the birdies kept coming. In the end, I managed to hit a couple of good putts which was nice," said Ilonen, who lost to Sergio Garcia in a playoff in Qatar earlier this year.

Karlsson opened with three pars in a row. He dropped in back-to-back birdies at four and five, and followed with four more pars. Around the turn, he posted three more birdies to move into a share of second place.

"It was nice, I'm very, very happy. I worked quite hard when I've been at home since the Nordea Masters, so it's been nice to keep it going," Karlsson stated. "I've done a bit of work with my coach and things are coming together quite nicely. The long game was very, very good today."

Siem bogeyed the second, but bounced back with a birdie on the par-5 fourth. He faltered to another bogey on No. 9. The German birdied five of the first six holes around the turn to soar up the leaderboard. He moved into a share of second place with a birdie on No. 18.

Carlsson had four birdies on the back nine, his first nine holes. After five straight pars from the first, he traded a birdie for a bogey at six and seven. Carlsson closed with a birdie on No. 9, his last.

NOTES: The top three players on the final leaderboard on Sunday that have not already qualified for the British Open, and finish in the top 10, will secure a spot in the field at Royal Liverpool ... Ilonen won twice in the 2007 season and won last year ... Matthew Fitzpatrick, playing in his first event as a professional, stumbled to a 1-over 72, which left him tied for 80th.