Spanish Grand Prix winner Nico Rosberg has declared that Mercedes have an edge on Ferrari in the development race.

The constructors' champions came under intense pressure from the Italian team in the first four races of the season, but they had a comfortable advantage in Spain.

Rosberg told reporters: "It's a big step in the right direction, a bit of a surprise, but it showed we have an awesome car at the moment. We won the development race this weekend so it is an important indication for the season."

Lewis Hamilton came second for Mercedes, ahead of Ferrari's Sebastian Vettel.