Iraqi government sources report that President Jalal Talabani has suffered a stroke.
The president's chief of staff, Nasser al-Ani, told state television that the president was in intensive care but was in a stable condition.
An earlier statement on the presidential website said that Talabani was hospitalized late on December 17 after suffering what it called "a health emergency."
A later statement said the emergency was due to a hardening of his arteries.
The president's office said "a specialized medical team" was taking care of him.
The president underwent heart surgery in the United States in 2008 and was treated for dehydration and exhaustion in Jordan in 2007.
Talabani founded one of the main Kurdish political parties, the Patriotic Union of Kurdistan, and became Iraq's first non-Arab president in 2005.
The presidency is a largely ceremonial post, though it does retain some powers under the Iraqi Constitution.
Based on reporting by AP, AFP, BBC, AP, and Reuters