JEREZ DE LA FRONTERA, Spain (AFP) - Mercedes began the 2015 Formula One campaign in the dominant fashion they became accustomed to last season, as Nico Rosberg went fastest in the morning session on Sunday's first day of testing in Jerez.

The German racked up 60 laps, registering a fastest time of 1min 23.106sec, ahead of Daniel Ricciardo in the Red Bull and Sauber's Markus Ericcson.

Sebastian Vettel was the first man out on the track, even sending a message by overtaking Rosberg in the pit lane on the way out for his first lap in the SF15-T Ferrari.

However, the four-time world champion was nearly three seconds down on Rosberg's time in his nine laps.

There were even more concerning signs for Fernando Alonso on his return to McLaren, as the new Honda-powered MP4-30 was the last car to go out and was over 17 seconds off the pace during the six laps he was on track.