Spanish motorcycling legend Angel Nieto has died aged 70 one week after he was left in a serious condition when his quad bike collided with a car, MotoGP announced in a statement.

Family and friends of the 13-time world champion had gathered at the Rosario Polyclinic hospital to be close to the 70-year-old after he suffered a massive cerebral edema - excess fluid on the brain - and required emergency surgery to relieve the pressure in his skull.

"The Nieto name remains synonymous with Spanish motorcycling and the 12 + 1 world champion will be deeply missed; forever remaining an inspiration to his nation and to the entire MotoGP paddock," the statement read.

"The MotoGP community extends its deepest condolences to Nieto's family and friends as we bid farewell to a true giant of motorcycling history who will be greatly missed."

Nieto was admitted to hospital on July 26 after he suffered serious head injuries when his quad bike collided with a car at a traffic circle in Santa Eularia, a town located in the centre of the Balearic island of Ibiza.

It is understood that hospital staff began to bring Nieto out of an induced coma on Thursday and that there had been no sign that complications would arise.

Nieto won 13 Grand Prix World Championships between 1969-84: eight in the 50cc category and five with 125cc engine capacity.

However, being extremely superstitious with a notorious fear of the number 13, he always referred to his championship tally as 12+1 and used those numbers in his autographs.