Sebastian Vettel topped the time charts on Formula One's return to action at the Belgian Grand Prix.

The four-time world champion, without a win since taking the chequered flag here at Spa-Francorchamps 12 months ago, led Charles Leclerc in a Ferrari one-two.

Lewis Hamilton was only sixth in the opening practice session after a power failure restricted his early running.

The London-born Alex Albon finished fourth, and within a tenth of his new team-mate Max Verstappen, on his debut for Red Bull.

Following its traditional summer shutdown, the sport sprang back into life on Friday morning, with Hamilton holding a commanding 62-point lead in his quest for a sixth world championship.

But the Briton endured a troubling return to the track after he reported a lack of power in the opening minutes.

Hamilton crawled back to the pits before his Mercedes team identified a problem with his throttle pedal.

The pedal was replaced by Hamilton's mechanics but the world champion's best time was then good enough only for sixth, slower than team-mate Valtteri Bottas and 1.4 seconds adrift of Vettel.

Remarkably, Ferrari have not won a race this season, but the high-speed Spa-Francorchamps circuit suits their machinery.

Vettel finished 0.214secs clear of team-mate Leclerc with Verstappen third, the Dutchman a best part of a second down on the Ferrari driver.

Albon has been promoted from Toro Rosso in place of Pierre Gasly for the second half of the campaign, and the 23-year-old will be pleased with his first run in the Red Bull car.

Albon will start at the back of the grid in Sunday's race, however, following changes to his Honda engine. Gasly, sent back to Toro Rosso after he was thrashed by Verstappen, ended the session in 18th.

British teenager Lando Norris finished 12th in his McLaren, two spots behind team-mate Carlos Sainz. Kimi Raikkonen brushed off a leg strain to finish 13th for Alfa Romeo.