Italian Marco Simoncelli suffered what appeared a serious injury after he lost control of his bike on the second lap and appeared to be hit by Colin Edwards and then Valentino Rossi as he slid across the track.

The 24-year-old's helmet came off in the collision and he was taken to the medical centre.

Newly-crowned champion Casey Stoner admitted watching the accident made him worried for Simoncelli.

"As soon as I saw the footage it just makes you sick inside," the Australian told BBC2.

"Whenever the helmet comes off that's not a good sign."

Tony Elias, Moto2 world champion, was praying the injuries to Simoncelli were not serious.

"We just hope Marco is ok - that's my wish," he said.

The organisers confirmed the race was cancelled, having halted it immediately after the incident.

A bulletin from the organisers said: "Race cancelled as the medical centre staff is focusing on treating Marco Simoncelli and track action cannot be resumed in the current circumstances."