Iraqi President Jalal Talabani is said to be in a coma in hospital after officials and media reported he had suffered a stroke.
A statement on his website said President Talabani was in a stable condition and was being treated for blocked arteries.
Well-placed Kurdish sources say he remains in a coma.
A veteran of the Kurdish guerrilla movement, Mr Talabani, 79, is Iraq's first president from the ethnic group.
He has struggled with his health in recent years and has often been treated abroad.
"Bodily functions are normal and the health condition of his excellency the president is stable," a statement on the presidency's website said.
The presidency said in an earlier statement that Mr Talabani's efforts to forge a consensus in Iraq and the "consequent fatigue and tiredness" had led to a "health emergency" that led to him being admitted to hospital on Monday evening.
Soldiers assigned to the presidential guard were deployed around Medical City, Baghdad's largest medical complex where Mr Talabani is being treated.
Senior government officials and politicians were seen entering the hospital to check on his condition.
Mr Talabani's chief of staff, Nasser al-Ani, told state television that the president was in intensive care but was in a stable condition.
A spokesman for Prime Minister Nuri al-Maliki told AP news agency that doctors were deciding whether to continue treating him in Baghdad or to fly him abroad for medical care.
Mr Maliki had visited the hospital to check on Mr Talabani's condition, he added.
The president had heart surgery in the US in 2008, and was treated for dehydration and exhaustion in Jordan in 2007.
Mr Talabani has lived through decades of conflict with the central government and other Kurdish groups, including a period in exile before the fall of Saddam Hussein.
He took over the mainly ceremonial presidency in the years after the 2003 invasion, and has often used the position to mediate between sectarian and ethnic groups.
Recently he brokered a deal between Baghdad and Kurdish groups to end a standoff on disputed areas on the border with the Kurdish self-rule area.
Mr Talabani and Mr Maliki were said to have met on Monday, and agreed to invite a Kurdish delegation to Baghdad for further talks.