Valentino Rossi breezes to victory at the Czech MotoGP.

Valentino Rossi takes out the Czech MotoGP easily, passing a fallen casey Stoner.

Italy's Valentino Rossi stormed to victory in the Czech Republic Grand Prix at Brno last night after defending world champion Casey Stoner crashed out early in the race.

Seven-time world champion Rossi was unchallenged on his Yamaha to claim his second consecutive win.

“Without Stoner's fall I probably wouldn't have won,” admitted Rossi, who opens up a 50- point lead in the world standings on Stoner after 12 of 18 races. A win is worth 25 points.

Spaniard Toni Elias, on a Ducati, finished second 15.005sec behind the Italian and Loris Capirossi, of Suzuki, was third at 21.689sec.

Stoner, who had battled flu-like symptoms on Saturday to claim his sixth successive pole position, was forced to withdraw after just six laps of the Brno circuit.

He fell on a right bend and slid across the track into the gravel when leading, one second ahead of Rossi. The Australian attempted to get back into the race but was forced out because of damage to his Ducati.

His compatriots fared much better, Anthony West fifth for Kawasaki and Chris Vermeulen sixth on a Suzuki.

In 250cc, Spain's Alex Debon, riding for Aprilia, made an audacious attack on the last lap to dramatically win ahead of compatriot Alvaro Bautista. Italian championship leader Marco Simoncelli was third.

Germany's Stefan Bradl, riding an Aprilia, achieved his first career win in the 125cc race.

The next race of the season will be the San Marino Grand Prix on August 31.