Three-time Formula One drivers' champion Niki Lauda underwent lung transplant surgery at Vienna's general hospital, the clinic said in a statement on Thursday.

According to media reports, Lauda, 69, had been in the hospital for the past week after cutting his vacation the Spanish island of Ibiza short to return to the Austrian capital. He was moved from the intensive care unit to a regular wing in the hospital before suffering a setback on Thursday.

"We ask for your understanding that the family will not make any public statements and request the privacy of the Lauda family," the statement said.

The hospital did not provide information on Lauda's condition.

Nürburgring crash

Lauda's lung has been impaired since he crashed at the 1976 German Grand Prix at the Nürburgring, where he was trapped in his flaming Ferrari car for 55 seconds. He suffered severe burns from the wreck and went into a coma shortly after getting out of the car.

He lost most of his right ear as well as hair on the right side of his head, his eyebrows and his eyelids. Incredibly, he returned to the cockpit 42 days later, missing only two races, but finished second in the 1976 drivers' championship to British driver James Hunt.

Lauda chose to limit reconstructive surgery to replacing his eyelids and getting them to work properly. He has also undergone two kidney transplants due to the crash.

Born in Vienna, the Austrian won four F1 titles in his career — 1975 and 1977 with Ferrari and 1984 with McLaren. He ended his career a year after his third championship. He was appointed as anon-executive chairman of the Mercedes racing team in 2012 after working with Ferrari and Jaguar.

His story is depicted in the 2013 film "Rush", in which his character is played by German-Spanish actor Daniel Brühl.

dv/pfd (dpa, SID)