Kimi Raikkonen fastest in first Bahrain GP practice

Ferrari's Kimi Raikkonen and Sebastian Vettel set the pace in first practice at the Bahrain Grand Prix as Mercedes hid their true form.

Raikkonen was 0.202 seconds faster than Vettel. Mercedes pair Nico Rosberg and Lewis Hamilton were only 15th and 16th.

Williams's Valtteri Bottas was third, from Toro Rosso's Carlos Sainz Jr and Red Bull's Daniel Ricciardo.

The second Toro Rosso of Max Verstappen was sixth, ahead of McLaren's Fernando Alonso and Sauber's Felipe Nasr.

Mercedes's unusual approach to the session - they normally dominate practice - was taken because conditions in the desert were very different from those that will prevail in qualifying and race.

The first session was held in the heat of the desert day, with the temperature soaring to 35C, while qualifying and race (on BBC One at 16:00 BST on Sunday) take place after sunset.

Since Vettel's victory in Malaysia two races ago, which was rooted in the Ferrari's more gentle use of tyres in hot conditions, Mercedes have been very aware of the need to ensure they are as prepared for the race as they can be.

And although the Bahrain race takes place at night, temperatures will still be high enough for Mercedes to be aware that Ferrari could mount a serious challenge.

Ferrari driver Sebastian Vettel finished second in the session

"Mercedes have got the speed but they were clearly thinking very much about the long runs," said BBC F1 analyst Allan McNish. "But, I tell you, Ferrari are in the game."

Vettel's session was hindered by an engine problem, which forced him to abandon his second run. He spent three-quarters of an hour in the garage before going out again, only for the so-far unspecified problem to recur.

But whatever the issue was, it was not serious enough to prevent the German setting the second-fastest time behind his team-mate.

McLaren-Honda had some encouragement from Alonso's pace, and from the car's apparent good performance in the corners, but there was bad news for team-mate Jenson Button, who spun on his first flying lap at Turn One because the engine cut out.

Although the car was recovered to the pits, Button did not take any further part in the session.

Britain's Jolyon Palmer put in a strong showing on his second practice outing as Lotus's reserve driver.

The GP2 champion was 14th fastest, just 0.4secs and two places off team-mate Pastor Maldonado.

The third Briton, Manor's Will Stevens, was 18th fastest, 1.3secs ahead of team-mate Roberto Mehri.

Bahrain GP practice results

Bahrain GP coverage details