Italian rider Marco Simoncelli has died after a horrific crash at the Malaysian MotoGP in Sepang.
The race was stopped after four minutes when Simoncelli's bike veered across the track at turn 11 into the path of Colin Edwards and Valentino Rossi.
The 24-year-old had his helmet knocked off and was hit by both other riders.
American rider Edwards also fell but escaped serious injury - while fellow Italian Rossi was able to return to the pits.
Simoncelli lay motionless on the track after the impact, while the race was immediately red-flagged.
At first officials were looking to restart the race before the extent of Simoncelli's injuries became clear.
Honda rider Simoncelli first entered MotoGP for the 2010 season and won his first pole position at the Catalunya race in June this year.
Simoncelli's first podium finish came in the Czech Republic in August when he finished third but he bettered that with a second-place finish at the Australian GP.
World champion Casey Stoner said: "As soon as I saw the footage it just makes you sick inside. Whenever the helmet comes off that's not a good sign."
The Italian started in the 125cc class in 2002 and moved up to the 250cc class in 2006.
He claimed the 250cc world title in 2008.