Biaggi fought off arch-rival Rossi

Biaggi, who started from pole, lost his lead to Rossi at the halfway point before fighting back for his first win of the season.

Brazilian Alex Barros was second with American Nicky Hayden in third while Rossi eventually finished fourth.

The result means Biaggi is now on 138 points, just one point behind Rossi in the championship standings.

Carlos Checa, joint world championship leader Sete Gibernau and Loris Capirossi all crashed out of third place in the first half of the race to allow Biaggi and Rossi to pull clear.

Rossi made his move at half distance but with seven laps to go, he slowed slightly and Biaggi was able to regain the lead which he never lost.

I would have risked crashing if I had pushed any harder Valentino Rossi

"When Valentino passed me, I gritted my teeth and waited to attack," said Biaggi.

"I caught my breath for a couple of laps and then returned the favour by waiting for a moment of weakness.

"Then on the last lap I closed all the doors on Barros, I didn't want to lose it in the last metres after such a great race, that would have been awful. It all paid off.

"I am obviously delighted, these 25 points change the standings and they fire us into an important second half of the season, which should be very hard-fought."

Rossi said: "The bike was going really well but the tyres were wearing on the left-hand side and I would have risked crashing if I had pushed any harder.

"It was difficult to steer the bike towards the end. Honda has made another step forward and we are a bit behind.

"We need at least another race to make improvements, however we have still taken a present of some points.

"Life is always a surprise. Max did really well and this has turned out to be one of Honda's tracks. Our bike consumed the tyres more than the Hondas here."

Northern Ireland's Jeremy McWilliams had his best finish of the season, picking up four championship points for 12th place.

Standings:
1 Rossi 139 points
2 Biaggi 138
3 Gibernau 126
4 Barros 79
5 Edwards 75
6 Hayden 70
7 Checa 62
8 Melandri 57
9 Capirossi 55
10 Tamada 54

250cc race results:
1 Daniel Pedrosa (Spa) Honda 41 mins 37.239 secs
2. Sebastian Porto (Arg) Aprilia 41:41.518
3. Alex De Angelis (San Marino) Aprilia 41:53.642
4. Hiroshi Aoyama (Jpn) Honda 41:54.008
5. Randy De Puniet (Fra) Aprilia 41:54.205
6. Roberto Rolfo (Ita) Honda 41:55.374
7. Anthony West (Aus) Aprilia 42:09.380
8. Fonsi Nieto (Spa) Aprilia 42:10.005
9. Franco Battaini (Ita) Aprilia 42:14.965
10. Sylvain Guintoli (Fra) Aprilia 42:15.327