The author was taken to a hospital on February 25 after showing symptoms of the disease upon returning from a book festival in Portugal, reported France 24.
Local newspapers in Spain had reported that he was in critical condition by March 10. But no further information was shared after this update.
Sepulveda, 70, was best known for his book 'The Old Man Who Read Love Stories' and was forced into exile by Pinochet's government in Chile.
President of Spain's Asturias region, Adrian Barbon said, "Health workers gave everything to save his life but he never got over the illness. My condolences to his wife and family."
Meanwhile, in Spain the death toll due to coronavirus crossed 19,000 on Thursday with 551 new deaths in the last 24 hours.
( With inputs from ANI )