Italy's Valentino Rossi, on a Yamaha, won the Czech MotoGP to extend his overall championship lead and move a big step closer to clinching a ninth world title.

After a thrilling head-to-head duel with Spanish stable-mate Jorge Lorenzo, Rossi profited from the latter's fall five laps from the finish to increase his lead to 50 points going into the final seven races. The next one is the Indianapolis MotoGP on August 30.

Lorenzo had passed Rossi three laps earlier but his spectacular tumble - from which he emerged unscathed although he angrily threw his gloves down and kicked out at his machine - handed Rossi a clear run through to the finish and a 102nd career victory.

The 30-year-old Rossi, nicknamed The Doctor, is now closing in on Giacomo Agostini's all-time mark of 122 race wins.

After crossing the line exuberantly on one wheel in 43min 08.991sec, he leapt over the barrier to celebrate with his crew.

Afterwards, he had time to offer a word of sympathy to Lorenzo - while insisting that he could not think of putting yet more title champagne on ice.

"It's really a shame for Jorge," said the Italian, noting that, despite his handsome lead "there's a long way to go. I have to stay focused."

Dani Pedrosa, of Honda, was second, 11.766 seconds adrift of Rossi while fellow Honda rider Toni Elias, who predicted a tough future as he is looking for a new team for 2010, completed the podium.

Italy's Marco Simoncelli, of Gilera, won the 250cc race as the world champion beat compatriot Mattia Pasini with Spain's Alvaro Bautista taking third place.

The win means the Italian can still retain legitimate hope of overhauling Honda's Hiroshi Aoyama, who currently leads the standings with 172 points to Aprilia racer Alvaro Bautista's 160 and 140 for Simoncelli, who now has three wins this campaign and won from pole yesterday.

Pasini missed out at the death after coming through from seventh on the grid to give Simoncelli a fine run for his money.

Nicolas Terol, of Spain, won the 125cc race in Brno ahead of compatriot Julian Simon and Andrea Iannone of Italy.

Terol grabbed the lead from the start and was never threatened after that as he recorded his first win of the year.

Top 10 riders

1. Rossi 212 points;
2. Lorenzo 162;
3. Stoner 150;
4. Pedrosa 135;
5. Edwards 112;
6. Dovizioso 107;
7. De Puniet 80;
8. Melandri 79;
9. Capirossi 77;
10. Vermeulen 72.