Stewart and Buchanan set the pace with seven-under 65s at Dunhill Links

MJ Dauffe and amateur Paul Harris lead the team event on 12 under, alongside Ivan Cantero and Tom Jermoluk.

With both pros and amateurs in action on Thursday, it was Scotland's Stewart who set the clubhouse lead first on Thursday afternoon at Carnoustie.

The 36-year-old, who was given a sponsor's invitation on Monday, strung together five birdies and an eagle without a practice round to set the target at seven under par around the Angus Links.

"It's easy to get yourself up for this event, isn't it?" said Stewart, who is playing in just his sixth DP World Tour start and first Alfred Dunhill Links Championship.

"It was fine. I played Monday, Tuesday, Wednesday, straight here and courses I know well anyway. Played here a lot in the past and just delighted to be part of the event.

"Today the putter was really good again which was nice. It's not been behaving as well as it usually has the last sort of couple of events. Again, the long game was good today and it was nice to see some putts go in on the back nine. "

Buchanan, who is also making his debut in the event this week, matched Stewart's 65 while playing Kingsbarns during his opening round.

"Pretty solid start to the week," the Australian said after his round.

"Obviously this is probably one of the easier courses out of the three, but yeah, good start.

"My approach play was really good. I think I basically hit 18 greens. Took a little bit of stress off myself and yeah made a few birdies."

The pair sit one shot ahead of South African pair Casey Jarvis and MJ Dauffe, with a group of seven players behind them on five-under-par.

Last week's champion Matt Fitzpatrick held an early share of the lead and will head into Friday at Kingsbarns on four under, alongside a group of 11 other players that includes Ryder Cup team-mate Sepp Straka.