Former Indonesian leader Suharto has pneumonia and is developing a potentially deadly blood infection, according to his medical team.
Suharto ruled Indonesia with an iron fist for three decades
Although he had recently shown signs of improvement, his doctors said that "anything could happen".
The 86-year-old was rushed to hospital in Jakarta on 4 January suffering from anaemia and low blood pressure.
Suharto ruled Indonesia with an iron fist for 32 years until popular protests forced him out in 1998.
Over the past 10 years, he and his family have been forced to deny allegations that they siphoned off billions of dollars while in power.
RISE AND FALL OF SUHARTO
Born in Java, June 1921
Comes to power in 1965 after alleged Communist coup attempt
Formally replaces Sukarno as president in March 1967
Modernisation programmes in the 70s and 80s raise living standards
East Timor invaded in late 1975
Asian economic crisis of the 1990s hits Indonesian economy
Spiralling prices and discontent force him to resign in May 1998
Judges rule he is unfit to stand trial for corruption in 2000
Transparency International says he tops the world all-time corruption table in March 2004
Suharto suffered multiple organ failure on Friday and doctors have said they are amazed by his strength.
He has developed pneumonia in one of his lungs and the blood infection sepsis.
Muhammad Munawar, a cardiologist treating Suharto, earlier told domestic radio that anything could happen.
"Every minute we must observe developments and frankly, these can go up and down," he said.
Suharto has had a series of high-profile visitors in hospital, including Malaysia's former Prime Minister Mahathir Mohamad.
Suharto supporters credit him with leading his country from poverty to relative prosperity, but he is also accused of repression and responsibility for severe human rights abuses, as well as corruption.
However, he never faced trial on any of these allegations - his lawyers argued that he was too ill.
He has been in and out of hospital in recent years with a series of strokes and other illnesses.