Casey Stoner crashed out for the second race in succession to gift Valentino Rossi victory in the San Marino MotoGP.

Stoner retired after losing the front end of his Marlboro Ducati to hand his Italian rival the win and increase his commanding lead in the championship race.

The Fiat Yamaha rider's first MotoGP win at his hometown event moves him onto 262 points, 75 ahead of Stoner with just five races remaining.

Jorge Lorenzo claimed second place to complete a Fiat Yamaha one-two while the in-form Tony Elias bagged a second podium in succession for Alice Ducati.

Rossi's win was his third in a row following victories in the United States and the Czech Republic, and sees him equal Giacomo Agostini's premier class record of 68 wins.

"It is incredible to get three in a row," Rossi told BBC Sport. "It was another great battle with Stoner - we know that Stoner is very strong.

"To win my 68th race in my hometown is incredible. I saw Giacomo Agostini before the race, and he was laughing. So I said to him I would try to win today.

"We have a great advantage and we are one race closer to the title.

"Last year, in these three races, I took nine points, this year 75, so it's not too bad."

Stoner had earlier led away confidently from his seventh pole position in succession and opened up an immediate gap over Honda Repsol's Dani Pedrosa, who had rocketed past Rossi off the line.

The defining moment of the race arrived on lap six when Stoner, just as in Brno last time out, lost control of his bike under no pressure and slid into the gravel trap, effectively handing the championship to Rossi who went on to win by three seconds.

Further back, Tech 3 Yamaha's James Toseland climbed from ninth to sixth by lap eight before passing Andrea Dovizioso to set himself on target for his best finish in MotoGP.

The Briton could not hold onto the position, however, as the charging Rizla Suzuki of Chris Vermeulen swept past with six laps remaining.

Vermeulen closed on Pedrosa but could not overhaul the Spaniard for fourth, while Toseland had to dig deep to hold off Loris Capirossi and Dovizioso on the run to the flag.

Earlier, Spaniard Alvaro Bautista won the 250cc race from 11th on the grid while Gabor Talmacsi took the honours in the 125cc event.