LOS ANGELES (AFP) — Viktor Hovland opened a one-shot lead at the PGA Tour Championship on Saturday as Rory McIlroy surged back into contention in the final event of the FedEx Cup playoffs.

Playing with a black ribbon on his cap to mourn the passing of King Harald, Hovland made four birdies on the final six holes to finish 15-under par, one clear of Ryan Gerard.

With a $10-million top prize at stake, world number one Scottie Scheffler was among a quartet on 12-under par, while McIlroy finished a further two shots back after a superb seven-under-par 63 — the day's joint lowest round.

Hovland had briefly pulled clear of overnight co-leader Gerard with a birdie on three, but bogeyed the next hole and spent most of Saturday trailing the American.

Gerard made birdies on six, seven and 12 for a two-stroke advantage, before the Norwegian began his charge with a curling downhill putt on 13.

Hovland, the 2023 Tour Championship winner, followed that up with more birdies on 15, 17 and 18.

"When I've given myself an opportunity, I've taken it. And here we are — after 54 holes, we're in a good spot," he said.

"If I can keep hitting fairways and give myself a few more looks, I think I'm pretty deadly with that putter," Hovland added.

Despite being tied third, Scheffler cut a frustrated figure missing several good birdie putts, but scored a bogey-free 66.

His expletive-laden rant had to be muted by broadcasters after one attempt broke unexpectedly on 13.

"I was close to the putts man," he said.

"It's challenging to hole putts. I'll just keep giving myself the looks, and hopefully they'll drop tomorrow," Scheffler added.

Scheffler was joined on 12-under by Adam Scott, Ludvig Aberg and Chris Gotterup.

Australia's Scott -- the oldest player in the field at 46 -- is also seeking his second Tour Championship win, a full two decades since his maiden victory at East Lake Golf Club in Atlanta, Georgia.

Sweden's Aberg opened with a double bogey but finished with three straight birdies, while Gotterup briefly held the lead with a birdie on six before losing pace.

Meanwhile, McIlroy stormed back into contention with a whopping nine birdies.

The three-time Tour Championship winner started the day seven strokes off the lead, having suffered an embarrassing double bogey Friday when consecutive chip shots rolled back downhill to settle at his feet.

But three straight birdies from 15 through 17 -- all with putts of more than 12 feet -- propelled McIlroy briefly into the co-lead.

"I putted a lot better. I think I lost maybe a combined three on the greens over the first two days and I probably gained over three on the greens today," McIlroy said.