Hiroshi Aoyama has won the 250cc Dutch TT and taken the world championship lead after surviving a dramatic clash with title rival Alvaro Bautista.

The pair had worked their way steadily up the order to sit second and third behind reigning 250cc world champion Marco Simoncelli by the halfway point of the 24 laps.

Both blasted past the Gilera rider soon after and disappeared into the distance, with Bautista shadowing Aoyama's Honda in preparation for a last lap showdown.

But the race was decided just before then, when Aoyama pushed too hard into the final chicane on the penultimate lap and ran slightly wide, killing his momentum. Bautista came barreling in behind on the racing line and slammed into the back of the slowing Aoyama, launching his Aspar Aprilia into the air with such force that the front tyre was knocked off the rim.

Bautista was down and out, while Aoyama nursed his damaged machine home for his second victory of the season and now leads the unlucky Bautista by 13 points.

Simoncelli had lost out to pole sitter Hector Barbera in the closing stages, but Bautista's exit meant the 2010 MotoGP rider claimed an unexpected podium.

The 250cc World Championship does not take part in the forthcoming Laguna Seca round, meaning their next event will be the German Grand Prix on July 19.

Race results - Assen:

1. Aoyama (Honda)
2. Barbera (Aprilia) +8.487sec
3. Simoncelli (Gilera) +10.339sec
4. Espargaro (Aprilia) +11.383sec
5. Locatelli (Gilera) +11.596sec
6. Debon (Aprilia) +14.265sec
7. Abraham (Aprilia) +17.982sec
8. Faubel (Honda) +19.012sec
9. Wilairot (Honda) +20.926sec
10. de Rosa (Honda) +21.033sec

Markham (Honda) DNF