Austrian President Thomas Klestil (search) was in very critical condition Tuesday after facing a "multiple organ failure," doctors said.

A day earlier, Klestil's heart stopped beating as he was being flown by helicopter to Vienna's General Hospital after being found unconscious. He was admitted in critical condition, and doctors said they could not rule out brain damage as a possible result of lack of oxygen before hospital staff got his heart functioning again.

In a statement Tuesday, doctors said the president's health has "deteriorated further" and that he had suffered "multiple organ failure." They said he has deteriorating functions of key organs like heart, lung, liver and kidney.

"We are very worried about his condition," said doctor Christoph Zielinski who described Klestil's condition as "dramatic."

"Today is critical on whether the president will survive," he said.

Klestil was found early Monday at his suburban villa by security guards, who used a defibrillator to revive the 71-year-old president.

By Monday evening, Klestil was heavily sedated with his temperature medically lowered as doctors worked to stabilize his lung functions, hospital staff told the Austria Press Agency. They said he would remain sedated for at least 14 days.

Klestil suffered from a severe case of pneumonia in 1996, and his lung problems had turned serious again in recent days.

Klestil's second and final six-year term ends Thursday, when Heinz Fischer (search) takes over as president. A packed schedule for Klestil's last days in office was canceled, and Chancellor Wolfgang Schuessel (search) assumed presidential duties until the hand over.

While the post is mostly ceremonial, the president is commander in chief of the country's military, and the constitution gives the head of state the power to reject nominations for Cabinet ministers or even to remove them from office — something that has rarely been done.

Klestil, a career diplomat who earlier served as Austria's ambassador to the United States and to the United Nations, was widely credited with helping restore Austria's credibility following a controversy over the Nazi German wartime service of his predecessor, Kurt Waldheim (search).

On a trip to Israel during his first term, Klestil expressed sympathy with victims of the Holocaust in a speech to the Knesset, making a reference to Austria's role in the atrocities — only one of the numerous times he spoke out against Nazi horrors and his country's part in them.