SAN FRANCISCO (AFP) — Australian Lucas Herbert reeled off six straight birdies before a closing par to grab a two-stroke lead after Thursday's first round of the US PGA Tour's Fortinet Championship.

The 27-year-old made 10 birdies against a lone bogey to fire a nine-under-par 63 at Silverado in Napa, California.

That matched his career-low 18-hole PGA Tour score, which he first managed in last year's final round of the Zozo Championship.

"Found a little groove there," Herbert said.

"It felt like anything I did poorly seemed to work out nicely for me and the good shots got rewarded as well."

"Felt like I played okay and just got a lot of good breaks and capitalized on chances as well."

Herbert, who took a seven-week break following a missed cut in July's British Open, added: "I felt like coming here I was ready to play again."

South Korea's Kim Seong-hyeon was second after a bogey-free 65.

Six players were a further shot back including England's Harry Hall and South Korea's Kang Sung-hoon.

Herbert's only US PGA Tour title came at the 2021 Bermuda Championship.

But he is a three-time winner on the DP World Tour, his most recent in April when he won the ISPS Handa Championship in Japan with a birdie on the second playoff hole to defeat Canada's Aaron Cockerill.

After birdies at the third and par-five fifth holes, Herbert took a bogey at six but answered with a 28-foot birdie putt at the seventh and began the back nine with a 24-foot birdie putt.

His epic birdie run, twice as long as his prior PGA career-best streak, began with tap-ins at the par-five 12th and par-four 13th.

He then sank birdie putts from nine feet at 14, just inside five feet at the par-five 15th and 16 feet at 16 and the par-three 17th.