Spain's Marc Marquez on a Derbi won the San Marino 125cc Grand Prix here on Sunday for Spain's 21st consecutive victory in the category.

The 17-year-old beat home compatriots Nicolas Terol (Aprilia) and Efren Vasquez (Derbi).

Victory assured Marquez of staying top of the overall standings as he extended his lead over Terol to nine points.

Britain's pole sitter Bradley Smith failed to benefit from his starting position and came in fourth.