"Nicky Hayden (Red Bull Honda World Superbike Team) has been involved in a training incident which saw the American be hit by a auto when he was out training on his bicycle".
An initial statement from the hospital on Wednesday evening said he had suffered a cerebral edema and several fractures, including to his leg.
Photographs published by local media outlets showed substantial damage to the front windscreen of the vehicle and the bicycle.
The medical teams are working hard, and we will provide updates as soon as they are available.... Once Nicky's condition was stabilised, he was transferred to Maurizio Bufalini Hospital in Cesena and remains in the hospital's intensive care unit.
Doctors are reportedly considering whether to operate on the stricken rider.
"Following the incident, emergency services were called to the scene and Hayden was transported to the local hospital".
Reigning champion and championship leader, Kawasaki Racing Team rider Jonathan Rea, sent a message of support for Hayden on Twitter.
Hayden was riding with a group when he was struck by a vehicle.
The 2006 MotoGP Champion was reportedly hit by Peugeot auto while bicycle training with a group of others along the Rimini coastline.