Zanardi transferred to intensive care as condition becomes unstable.

Alex Zanardi, the ex-Formula One driver and Paralympic champion, has been transferred to intensive care due to his "unstable clinical conditions," just days after he was moved to a specialist neuro-rehabilitation centre.

The 53-year-old Italian sporting legend was left battling for his life after receiving serious head injuries in a collision with a truck during the Obiettivo Tricolore relay race between Pienza and San Quirico d'Orcia in Tuscany on 19 June.

• Alex Zanardi in critical condition after road accident

Zanardi underwent emergency neurological surgery and spent the subsequent four weeks recovering in hospital, in an artificial coma.

On 21 July he was moved to a rehabilitation centre after his sedation was ended however it was confirmed today, 24 July, that he has been transferred to the intensive care unit of Milan's S. Raffaele hospital.

Hospital authorities said in a statement that "no further information on the case will be released."

• Pope hails Alex Zanardi's 'lesson of humanity'

Zanardi is a hugely popular figure in Italy who gained widespread respect for reinventing himself after having both legs amputated following a horrific racing-car crash in 2001.

On 23 June Pope Francis sent a handwritten letter to Zanardi, who has won a total of four Paralympic gold medals, praising his good example for living life to the full and for providing a "lesson in humanity."