Paralympic champion Alex Zanardi underwent a third neurosurgical operation on Monday with doctors saying he remained in grave condition after a serious accident in early June.

Zanardi is a former Formula One driver who had both his legs amputated after a motor racing accident two decades ago, and suffered serious head injuries when he lost control of his handbike during a race on a Tuscan road crashing into an oncoming truck in June. 

Doctors at the Sianna hospital where Zanardi was treated say the operation went well i terms of facial reconstruction, but there remain grave concerns about his neurological condition.

The 53-year-old suffered head injuries with multiple facial factures in the crash on June 19 that has gripped Italy.

Zanardi has become one of the great figures in disabled sports following the 2001 motor racing accident on the Lausitzring track in Germany.

He raced for Jordan, Minardi and Lotus in F1 in the early 1990s before switching to the CART championship in the United States where he was series champion in 1997 and 1998.

He returned to F1 with Williams in 1999 before heading back to CART.

Zanardi brought back two gold medals from the 2012 London Paralympic Games and four years later won two more in Rio de Janeiro.

He won the Rome marathon in 2010 and the New York race the following year.