Leclerc was 0.082 seconds ahead, with Sebastian Vettel third in the second Ferrari, 0.543secs off the pace.

Mercedes drivers Valtteri Bottas and Lewis Hamilton were fourth and fifth but used slower tyres.

Red Bull's Alexander Albon was sixth, nearly a second slower than Verstappen, and ahead of Renault's Nico Hulkenberg.

Bottas was 0.7secs off Leclerc, and Hamilton 0.2secs further back. But Leclerc, Vettel and Verstappen all ran the 'soft' tyres to set their fastest times, while Bottas and Hamilton used the 'medium', so it is hard to draw any conclusions from their headline lap times.

The key question ahead of the weekend is whether Ferrari can keep up the strong performance they showed in scoring a one-two in Singapore last weekend, on a circuit where they had not expected to be strong.

Sochi's flat and uninspiring track offers a chance to see the performance of the aerodynamic upgrade Ferrari introduced in Singapore on a more 'normal' circuit, and therefore a more rounded indicator of its potential effect on the team's general level of performance.

And for Vettel, this race offers a chance to prove that he can continue his return to form, following his first win for more than year.

Hamilton is concerned that Ferrari's step forward means they will be tough to beat for the rest of the season, assuming it means their cornering performance has improved to go along with their straight-line speed advantage.

Leclerc has scored more points than anyone else in the five races since the German Grand Prix, but he does not seem to be a threat to Hamilton in the championship, given the Briton's huge lead.

Ricciardo hit the wall at the end of the session

It was a generally uneventful session, although Daniel Ricciardo spun and crashed at Turn 10 at the very end. The Australian was able to drive back to the pits with a broken rear wing.

And Robert Kubica had a spin in the Williams, and Toro Rosso's Daniil Kvyat stopped on track early on with a problem with the brand new Honda engine that has been fitted to his car for this weekend.

The Russian already has a grid penalty that will mean he has to start from the back, so if Honda needed to introduce a second new engine for the weekend, it would make little difference.

The other Honda-engined drivers - Verstappen, Albon and Toro Rosso's Pierre Gasly - also have grid penalties, but only drop five places.

Toro Rosso's Pierre Gasly will drop five places on the grid after the team and Red Bull took an engine upgrade from Honda

Gasly's team-mate Daniil Kvyat will start at the back of the grid due to the engine penalty. The Russian driver managed just five laps of the first session before his Toro Rosso broke down