Italian media report that he was being treated for multiple injuries, including a broken shoulder, after being transported by helicopter from a track in Sagittario to Rome on Friday. The Ansa news agency says the 45-year-old Biaggi was conscious after the accident.
Biaggi won world titles in 2010 and 2012 and was also champion four times in the 250cc class of the MotoGP series. He was a three-time runner-up in the 500cc and MotoGP class. He was training with two young Moto3 drivers that he manages.
The accident comes less than a month after the former MotoGP world champion Nicky Hayden died after he was hit by a car while training on his bicycle in Italy.