Sergey Sirotkin led SMP Racing to a one-two finish in opening practice for the 6 Hours of Spa-Francorchamps on Thursday, finishing almost two seconds clear of the field.

After moving into the FIA World Endurance Championship following his exit from Formula 1 at the end of last year, Sirotkin managed to lay down a marker early in his second race weekend in the series in SMP Racing's #17 BR Engineering BR1 AER at Spa.

A fastest lap time of 1m56.264s saw Sirotkin finish 1.9 seconds clear of the field in FP1, with new arrival Stoffel Vandoorne finishing second quickest in the sister #11 SMP Racing entry.

Regular LMP1 pace-setter Toyota Gazoo Racing took third and fourth in FP1, with Sebastien Buemi leading its charge in the #8 TS050 Hybrid, 2.4 seconds off Sirotkin's time as Mike Conway set the fastest time in the #8 Toyota.

Both Toyota cars regularly set sector times faster than the SMP entries, though, hinting at more pace being in hand for the remainder of the weekend.

Rebellion Racing finished fifth and sixth in class with its pair of R13 Gibsons, while ByKolles Racing made its return to the WEC after missing the last round at Sebring due to a change in engine supplier.

Nicolas Lapierre took top spot in the LMP2 class for Signatech Alpine Matmut in the #36 Alpine A470 Gibson ahead of Jean-Eric Vergne for G-Drive Racing, with Racing Team Nederland's Giedo van der Garde completing the top three in class.

Aston Martin Racing finished P1 in GTE-Pro through Maxime Martin in the #97 Aston Martin Vantage AMR, with Harry Tincknell taking second for Ford Chip Ganassi Racing, setting an identical lap time to Martin late in the session.

Ben Barker's early time in the #86 Porsche 911 RSR gave Gulf Racing top spot in GTE-Am ahead of Spirit of Race and Dempsey-Proton Racing.

GTE-Am team TF Sport received a black flag midway through the session due to a constant abuse of track limits, but was permitted to return to the track before the end of FP1 after the team manager met with the race stewards.