(AFP) - Reigning US Open champion Dustin Johnson fired a six-under 66 on Thursday to seize a share of the lead at the PGA Tour's Canadian Open at Glen Abbey Golf Club.

The 11-time PGA winner made seven birdies, an eagle, a bogey and a double-bogey to move into a tie atop the leader board with Luke List at the Toronto-area course.

"It's firm and fast," said world No. 2 Johnson.

"It's definitely tough to get the ball close to the hole. You've really got to land the ball on your numbers. With it being as windy as it was today, it was tough to do that."

Defending champion and world No. 1 Jason Day opened with a three-under 69 and is three shots back of the leaders. He is seeking to become the first repeat winner of the Canadian Open since Jim Furyk in 2006 and 2007.

Johnson, who won the US Open last month at Oakmont, is making his fourth start in the Canadian Open. He has had mixed results in the event, withdrawing in 2008, missing the cut in 2014 and finishing tied for second in 2013.

Johnson is Canada's adopted son as he is engaged to the daughter of Canada's greatest sports hero, NHL legend Wayne Gretzky. Johnson and Paulina Gretzky have an 18-month-old son.

List carded birdies on five of his first nine holes. He added another at the second hole en route to a bogey-free 66, matching his career-low round on the US PGA Tour.

"I was very fortunate that the first five holes there wasn't much wind at all and then it kind of picked up," said List, who is coming off missed cuts in five of his past seven starts.

Canada's Jared du Toit, Chesson Hadley, Kelly Kraft and Jon Rahm are tied for third at five-under 67.

Du Toit, an amateur, eagled the par-four 17th hole, then made a birdie on 18. Hadley made six birdies and one bogey. Kraft played the six-hole stretch beginning at the 13th in six-under.

Rahm is hoping to become the first to win the Canadian Open in his debut since Chez Reavie in 2008.