Nico Rosberg ensured Mercedes ended the opening day of running for the Bahrain Grand Prix on top of the pile by posting the quickest time in second free practice for the F1 season opener.

Rosberg posted a best time of 1min 55.409secs early on in the 90 minute session and remained unbeaten as the majority of teams elected to focus on a series of longer runs in preparation for the race on Sunday.

Rosberg was followed on the times by McLaren's Lewis Hamilton - despite the Briton reporting severe tyre wear on the harder compound Bridgestone tyres after a matter of laps - while Michael Schumacher was third in the second of the Mercedes cars. Jenson Button rounded out the top four as Mercedes-powered cars dominated the top of the time sheets.

Sebastian Vettel was fifth quickest for Red Bull, albeit more than a second off the outright pace, despite a number of trips across the run-off area exiting the final corner, although his session was better than that endured by team-mate Mark Webber. He ended the session down in 17th place after being sidelined by a driveshaft issue on his RB5.

Nico Hulkenberg was sixth quickest for Williams ahead of the Ferrari's of Felipe Massa and Fernando Alonso - which were split on the times by the Renault of Vitaly Petrov in an encouraging eighth place. The top ten was completed the first of the Saubers, in the hand of Pedro de la Rosa.

Aside from Webber, there were issues for both Toro Rosso drivers, with Jaime Alguersuari running wide on the new section of circuit created for this year's race and narrowly avoiding the barriers and Sebastien Buemi failing to set a time after running into a mechanical issue with his car.

Heikki Kovalainen was quickest for the newcomers as he put his Lotus 18th on the timesheets, just ahead of team-mate Jarno Trulli as the team lapped more than a second clear than Virgin Racing. Timo Glock was quickest of the two VR-01s, despite managing just a handful of laps.

Bruno Senna was able to complete some meaningful running for HRT, posting his fastest lap on the final lap of the session but still ending up more then eleven seconds off the pace. The Brazilian then suffered a spin at the first corner after the chequered flag had flown, with replays suggesting that he had lost a wheelnut from the right rear.

Team-mate Karun Chandhok failed to hit the track as the team faced delays in getting his car ready, meaning the Indian will have to wait until final practice to make his debut on an F1 race weekend.