Ailing Cuban leader Fidel Castro is in "very grave" condition after three failed operations and complications from an intestinal infection, a Spanish newspaper said Tuesday.

The newspaper El Pais cited two unnamed sources from the Gregorio Maranon hospital in the Spanish capital of Madrid. The facility employs surgeon Jose Luis Garcia Sabrido, who flew to Cuba in December to treat the 80-year-old Castro.

In a report published on its website, El Pais said: "A grave infection in the large intestine, at least three failed operations and various complications have left the Cuban dictator, Fidel Castro, laid up with a very grave prognosis."

Cuba has released little information on Castro's condition since he temporarily ceded power in July to his brother, Defence Minister Raul Castro, until he could recover from emergency intestinal surgery, prompting much speculation and rumour in the country and around the world.

El Pais's report, which could not immediately be confirmed, was a rare detailed description from a major media outlet about Castro's condition.

The U.S. government had speculated that Castro could suffer from cancer — a supposition denied by Sabrido. Some U.S. doctors believed Castro was suffering from diverticular disease, which can cause bleeding in the lower intestine, especially in people over 60. In severe cases, emergency surgery may be required.

Newspaper says Castro had intestinal bleeding

That idea was supported by El Pais, which reported that its sources said Castro had suffered a bout of the disease.

"In the summer, the Cuban leader bled abundantly in the intestine," El Pais reported. "This adversity led him to the operating table, according to the medical sources. His condition, moreover, was aggravated because the infection spread and caused peritonitis, the inflammation of the membrane that covers the digestive organs."

A statement attributed to Castro was released on New Year's Eve, saying his recovery was "far from being a lost battle."

Cuban officials told visiting U.S. lawmakers last month that Castro does not have cancer or a terminal illness and will eventually return to public life, although it was not clear whether he would return to the same kind of absolute control as before.