A military source told Reuters Mubarak was "breathing" but would not give details about his status. Another Egyptian source who had been close to the presidency said: "He is okay."
"What is certain is that his state of health is declining drastically, in addition there is information that he is refusing to receive the required medical treatment," Asharq al-Awsat said in its online edition, quoting a former security official affiliated to the Egyptian military high command.
The Higher Military Council took over the country after Mubarak resigned on Friday following over two weeks of massive protests against his 30-year rule.
The Asharq al-Awsat report said Mubarak, 82, had refused advice to travel to Germany for treatment. He underwent gallbladder surgery there last year, and since then rumours about his health have frequently surfaced.
"Mubarak is refusing this (travel abroad)," the paper said, quoting its source. "He has asked those around him to allow him to die in his country, and I believe this is just a matter of time."
Mubarak had said in his final speeches to the nation, while still hanging on to office, that he would die in Egypt.
Speculation has swirled about Mubarak's health, including some talk that he may have already died.