NEW PROVIDENCE, BAHAMAS (AFP) - Golf world No. 1 Jordan Spieth aced the par-three second hole while England's Paul Casey fired a six-under-par 66 to share the lead after round one of the Hero World Challenge on Thursday.

Casey's bogey-free round put him alongside Americans Jimmy Walker and Zach Johnson atop the leaderboard at the 18-man event hosted by Tiger Woods.

Defending champion Spieth's shot of the day left him one stroke back on 67 alongside compatriots Bubba Watson, Bill Haas and Brooks Koepka and Australian Adam Scott.

Spieth, the reigning US Open and Masters champion, used a six-iron from 172 yards for his hole-in-one and followed with a bogey-free round that included birdies at the seventh and back-to-back at the 14th and par-five 15th.

Casey, who suffered two play-off losses on the USPGA Tour this season, enjoyed his tour of the Albany resort, making birdies at the par-five third, sixth and 15th holes.

He also opened and closed the back nine with birdies and added another at 13 to secure his play-off among the leaders.

It's the seventh appearance at the event for Casey, who shared third in 2010 and 2011, his most recent prior starts.