Marco Simoncelli's fellow Moto GP riders have paid tribute to the 24-year-old Italian, who died following a crash during the Malaysian MotoGP in Sepang earlier today.

The Italian's Honda teammate Casey Stoner led the tributes, saying: "I'm so shocked and saddened by the loss of Marco.

"When things like this happen it reminds you how precious life is. It makes me feel sick inside."

Compatriot Andrea Dovizioso said: "He seemed invincible. What happened seems impossible.

"I think of Marco's family and all the people dear to him, in particular his father and mother. I also have a child and what happened today is the hardest situation you can imagine."

Another Honda rider, Dani Pedrosa, spoke of his disbelief: "Many times we ourselves forget how dangerous this sport can be and, when you lose people on the way, nothing has any meaning.

"It's clear we all do what we like, what we love, but on days like today nothing matters."

Honda worldwide executive vice-president Shuhei Nakamoto said: "Marco was a very nice guy and a very talented rider."

Formula One driver Jenson Button tweeted: "RIP Marco ... Such an exciting talent lost. My thoughts are with his family, friends and everyone involved in MotoGP. Motorsport can be so cruel."

Staff at the Sepang circuit's medical centre worked hard to resuscitate Simoncelli but he was declared dead at 9.56am British time.