He was last heard from on June 12 when his voice was broadcast on a telephone call with Venezuelan state television. At the time, the president told the interviewer doctors had found no sign of of "malignant" illness.
An official statement from the Venezuelan government said Chavez had been operated on for a pelvic abcess on June 10 in Havana. At the time he was in Cuba on an official state visit.
However, the report quoted unnamed U.S. intelligence sources who said Chavez is currently in "critical condition, not grave, but critical, in a complicated situation."
According to the EFE news agency, the president's daughter Rosines and his mother Marisabel Rodriguez "urgently" were flown to Cuba in a Venezuelan air force plane either Wednesday or Thursday last week.
A number of media reports have said that Chavez is actually suffering from prostate cancer, although intelligence sources have not confirmed the reports.
On Friday, four "tweets" were sent on Chavez's Twitter account in what appeared to be an attempt to quiet rumors that his condition was grim.
"Tiday is the day of my army and the sun dawned bright. A big hug to my soldiers and my beloved people," he allegedly wrote. (read more)