Red Bull's Max Verstappen set the pace in the opening running for the Singapore Grand Prix as Valtteri Bottas crashed out.
Verstappen finished 0.167 seconds clear of Ferrari's Sebastian Vettel with Lewis Hamilton third, six tenths off the pace.
Bottas became the first driver to fall victim to the demanding Marina Bay Street Circuit after he lost control of his Mercedes through the right-handed Turn 19.
First session in Singapore complete ✅ Max is P1 with a 1:40.259 💪 Alex comes home P5 posting a 1:41.467 👊 #SingaporeGP pic.twitter.com/At6F9eHDN7 — Aston Martin Red Bull Racing (@redbullracing) September 20, 2019
Bottas, who is Hamilton's closest challenger for this season's championship, locked up under braking and slammed into the barriers on the opposing side of the track.
The Finnish driver was unscathed in the low-speed accident, but he sustained serious damage to the front of his car. The action was suspended for 10 minutes to retrieve Bottas' wounded machine.
His Mercedes mechanics will now face a race against time to get his car ready for the second session later on Friday.
"Sorry guys." Valtteri walks away, but that W10 is going nowhere fast#F1 #SingaporeGP pic.twitter.com/TCHlHcNIhf — Formula 1 (@F1) September 20, 2019
The incident will come as a major blow to Bottas, who heads into the final seven rounds 63 points behind Hamilton in the standings.
He had earlier been provided a warning when he grazed the wall and had to pit with a damaged wheel.
The slow-speed track is likely to play into Red Bull's hands and Verstappen impressed in the first session. However, the day's concluding running will provide a greater indicator of the order, with the action taking place at night, akin to the conditions for Saturday's qualifying session and Sunday's race.
Gearbox problem to be investigated on #Charles16's car. #FP1 #SingaporeGP pic.twitter.com/0kx3MoyanA — Scuderia Ferrari (@ScuderiaFerrari) September 20, 2019
Charles Leclerc arrived in Singapore as the sport's in-form driver following successive victories in Belgium and Italy.
But the Monegasque's weekend got off to an underwhelming start as a gearbox issue in his Ferrari restricted him to only a dozen laps. He finished 19th.
Alex Albon was fifth for Red Bull, 1.2 seconds down on team-mate Verstappen. Renault's Nico Hulkenberg finished sixth.
McLaren's Lando Norris ended his first action in Singapore in eighth, while fellow British novice George Russell propped up the order for Williams.
