Suharto was admitted to the hospital on Friday suffering from internal bleeding as well as heart, kidney and lung problems and his condition has fluctuated in the days since.
Mardjo Soebiandono, the head of the medical team, said Suharto was in a "highly unstable condition" and required "intensive monitoring".
The former five-star general had also been given a blood transfusion, he said, adding that visitors will no longer be allowed to see him because of his weak state.
|Doctors have stopped visitors from|
seeing Suharto [AFP]
Juniarti Hatta, a cardiovascular expert and a member of the medical team, later said the swelling in the former president's left heart chamber could lead to heart failure.
A family friend told Reuters that all Suharto's children and relatives are already gathered by his side.
Siti Fadilah Supari, Indonesia's health minister, said after visiting him late on Tuesday that he was conscious but seemed to be getting worse.
"It is not getting better," she said. "All of us are on alert."
Suharto, who suffered from various ailments in recent years including intestinal bleeding and strokes, faces charges of embezzling public funds and abuse of power while in office.
The sudden deterioration in his health condition had also prompted calls for legal proceedings to be dropped but the government earlier this week said it would press ahead with a civil case.