Bahrain GP: Ferrari F1 pair Raikkonen and Vettel set practice pace

With track temperatures well over 50 degrees early in the session, after using their first sets of mediums during the first 30 minutes, several teams opted to leave it very late before making their final runs.

By that time, the track temperature had dropped to the mid-40s, with both Raikkonen and Vettel jumping from the lower reaches of the timing screens to the top in the final 10 minutes.

First Vettel, who when he initially went out for his final run was told to ease off while a problem was solved, deposed Williams driver Valtteri Bottas from top spot, then Raikkonen outpaced him by two tenths.

With usual pacesetter Mercedes down in 15th and 16th places with Nico Rosberg and Lewis Hamilton, having both moved onto their second set of tyres earlier in the session and presumably concentrating on heavier fuel-load work, Bottas was able to hang on to third place despite a lockup at Turn 10 and a wild moment in the middle of the last corner on his best lap.

Carlos Sainz Jr was another driver who held back his second set of tyres, briefly jumping up to second before behind shuffled back to fourth ahead of the lead Red Bull of Daniel Ricciardo and Scuderia Toro Rosso team-mate Max Verstappen.

McLaren-Honda driver Fernando Alonso was among the drivers to move onto their second set of rubber relatively early on and briefly went fastest, ultimately ending up a strong seventh, just under eight tenths off the pace.

But it wasn't all good news for McLaren, with Jenson Button spinning at Turn 1 on only his third lap and ending the day last after failing to set a time.

Sauber had another solid session, with Felipe Nasr in eighth place, although team-mate Marcus Ericsson was unable to make a significant improvement on his second set of rubber after running fifth following the first 30 minutes, and ended up down in 17th behind the two Mercedes drivers.

Felipe Massa, in the second Williams, was 10th fastest, but only four tenths off team-mate Bottas, just behind the second Red Bull of Daniil Kvyat.

Force India driver Sergio Perez also had a brief spell in first position early in the second runs, but ended up 11th ahead of Lotus driver Pastor Maldonado, who had a run through the gravel at the last corner while on a lap on his second set of rubber having already improved his time.

Lotus reserve driver Jolyon Palmer made his second appearance on an F1 weekend, ending up 14th and within half-a-second of Maldonado after losing time in the first sector.

At the foot of the timesheets, Will Stevens was the quicker Marussia ahead of team-mate Roberto Merhi in 18th and 19th places.