Horror As Motorcyclist is Killed

And Button's Formula One teammate Lewis Hamilton wrote: 'My thoughts are with his family, friends and team at this extremely sad time. Another tragic loss at such an early age.'

Newly-crowned MotoGP champion Casey Stoner said: 'I'm so shocked and saddened by the loss of Marco. When things like this happen it reminds you how precious life is.

The Australian told BBC2: 'As soon as I saw the footage it just makes you sick inside. Whenever the helmet comes off, that's not a good sign.'

A message on the MotoGP website read: 'Marco Simoncelli succumbed to injuries sustained in Malaysia.'

Simoncelli's compatriot and Repsol Honda rider Andrea Dovizioso said: 'I watched the images and I'm shocked: in a race you fight and push hard and disaster is often around the corner.

'Marco was a strong rider and he always pushed hard. We raced together since we were kids, I saw him always pushing to the maximum, he crashed many times, but without major injuries, he was seemed invincible. What happened today seems impossible.'

The last death in MotoGP came at the 2003 Japanese Grand Prix, when Japan's Daijiro Katoh died from his injuries.

Medical director at Clinica Mobile Dr Michele Macchiagodena said at a press conference yesterday that U.S. rider Edwards had suffered a dislocated shoulder in the crash but it had been reset and he was 'fine'.

When asked about Simoncelli's helmet coming off, race director Paul Butler said at the press conference: 'I think if I may reply, that will be for another occasion. Quite clearly the consequences and circumstances surrounding the accident will be thoroughly investigated.'

Australian Formula One driver Mark Webber wrote on Twitter: 'R.I.P Marco A special talent that will be missed... Thinking of your loved ones, and all the motogp paddock..mark.'