Smith birdied his opening hole on Thursday and followed it with eight pars before picking up seven shots in the last nine holes to compile an eight-under-par 62 and enjoy a two-stroke lead over Germany's Matthias Schmid and Scotland's David Drysdale in the European Tour event.

"Not half bad," Smith said.

"Just everything came together really. I've been struggling with my iron play recently, but that and my wedge game and my putting were really, really good today. I'm not going to lie."

American Jennifer Kupcho is one of three tied at the top of the women's leaderboard. PHOTO: harles McQuillan/Getty Images.

Schmid turned professional after winning the silver medal as the leading amateur in The Open Championship.

"So far I like it a lot actually," Schmid said of his successful start in the paid ranks after finishing 47th at last week's Wales Open. "I've been dreaming to do this for a long time. Second event, I'm enjoying it a lot. It's great.

"Obviously with the silver medal a lot of things went well for me. That's I think how I could get into these tournaments, and I hope I can draw a few more invites."

Leading Australian man after the opening round was Maverick Antcliff, who shot a two-under par 68 to lie in joint-24th place, a shot clear of compatriots Dimitrios Papadatos and Blake Windred.

The ISPS Handa World Invitational, which is tri-sanctioned by the European Tour, LPGA Tour and Ladies European Tour, sees men's and women's tournaments taking place simultaneously.

Players will complete 18 holes at Galgorm Castle and 18 at Massereene Golf Club before a halfway cut is made in each tournament, with a further cut after 54 holes to the top 30 players and ties.

In the women's event, Scotland's Gemma Dryburgh carded a seven-under-par 66 to share the lead with American Jennifer Kupcho and South Korea's Chella Choi, with England's Charley Hull and Georgia Hall two shots off the pace.

Top Australian was Su Oh with her four-under 68 at Massereene putting her in joint-ninth place, while Sarah Kemp, fresh from her impressive Evian Championship, shot a three-under 70 at Galgorm.

Steph Kyriacou was on two-under after her round at Massereene.