Ferrari driver Kimi Raikkonen leads in Spain

Kimi set the pace during practice at the Spanish Grand Prix.

McLaren's Lewis Hamilton was more than half a second slower.

But Renault enjoyed an encouraging day as Nelson Piquet Jr and Fernando Alonso came second and third in the afternoon.

Raikkonen's Ferrari team-mate Felipe Massa was second quickest during first practice, but finished fifth in the second.

During the first session, world champion Raikkonen, who just shaded his Brazilian team-mate, was 0.543 seconds clear of Hamilton's McLaren in third place.

Things got worse for the Briton in the afternoon as he ended 0.750 seconds down on Raikkonen, with even Force India's Adrian Sutil ahead of him in 10th.

Friday practice sessions are notoriously unreliable indicators of form, however, and Saturday's qualifying is a much more reliable indicator of form.

But the performances of Piquet Jr and double world champion Alonso hinted at an upturn in form for Renault, who have been off the pace so far this season.

They have introduced some new parts to the car for this race and are optimistic of a step forward.

Ferrari's apparent pace will be a concern for McLaren and Hamilton, who have struggled compared to their title rivals in the last two races.

McLaren have said that only after this race will a true picture emerge of the cars' relative competitiveness for the season and will be hoping they are much closer to Ferrari come race day.