Gasly lost control at the last corner and smashed into the barrier on the outside of the track, badly damaging his Red Bull. The Frenchman was unhurt.

Leclerc was 0.124 seconds quicker than Sebastian Vettel and 0.146secs ahead of Mercedes' Lewis Hamilton on a hot day.

Ferrari were first and second in both sessions and looked in good shape.

But conditions are expected to be cooler over the weekend, and rain threatens.

Hamilton's team-mate Valtteri Bottas was 0.662secs off the pace in fourth, ahead of Red Bull's Max Verstappen.

The Dutchman was 0.684secs slower than Leclerc and Red Bull looked to be in less of a good shape than they were in the past two races in Austria and Silverstone, at least on the evidence of Friday.

Gasly's crash was another blow for him, after a difficult season that has led to questions about his future in the team.

A strong performance at Silverstone had looked to be a turning point, but he had been struggling for pace - he ended the session only 15th fastest - even before his accident, which happened on his race-simulation run in the second part of the session.

Meanwhile, the day was encouraging for Ferrari, as not only were they quickest on a single lap, Leclerc's race-simulation run on the soft tyre was every bit as quick as Hamilton's.

However, conditions are expected to be very different at the weekend, with a drop in temperature form the mid 30Cs to the mid-20Cs, with the potential for rain as well.

Mercedes are celebrating 125 years in motorsport and their 200th Formula 1 start with a special white livery

Behind the big three, Haas' Romain Grosjean, in sixth, and Racing Point's Lance Stroll, in seventh, performed strongly.

It was an especially encouraging performance from Racing Point, who have introduced a major aerodynamic upgrade for this weekend after a dispiriting and disappointing first half of the season.

Grosjean is running the Haas in its specification from the first race of the season, while team-mate Kevin Magnussen, who was only 18th fastest, has the team's latest aerodynamic upgrade.

The idea is to compare the two cars' performance in an attempt to understand why Haas have shown such inconsistent performance this season, especially struggling to get the best out of the tyres in race trim.

Rounding out the top 10, Alfa Romeo's Kimi Raikkonen was eighth, ahead of Renault's Nico Hulkenberg and the second Racing Point of Sergio Perez.

"It has not been the best of days in terms of the heat," said Hamilton. "These tyres don't like high temperatures. It's about trying to keep the tyres in the working range - they are always overheating. That was the main issue today but everyone is in the same boat.

"If it's gonna rain, this is kind of a waste of a day. I don't feel like we learned much today anyway. It's so hot. If it's cooler on the weekend and it's dry nothing from today really applies. The tyres will come back towards us. Everyone will be quicker and more comfortable."

Watch the paintwork! Bottas lost control during first practice at the same corner at which Vettel crashed at last year

The heat was intense for some of the crowd, with just one lone fan braving the uncovered part of the grandstand

Turnaround? Ferrari were first and second in both sessions