Medical treatment — including dialysis — has halted Prince Rainier III's (search) deterioration, the royal palace said, and he remained in stable condition Monday.

In a cryptically worded health update, Rainier's doctors said treatment stopped the decline of his internal organs. His health is "still worrying but remains stable," the palace's statement said.

Asked about the statement, palace spokesman Armand Deus said doctors placed the prince on a dialysis machine Sunday evening to clean his blood, which appeared to help his condition. He could undergo more dialysis in the future, the spokesman said.

Monday's announcement marked a new stabilization in Rainier's condition, just two days after doctors said the 81-year-old monarch's key internal organs had been "progressively deteriorating."

On Sunday, three doctors for Rainier offered a first sliver of optimism, saying that his lung, kidney and heart functions had stopped declining.

The prince was conscious, but under sedation, for at least a second straight day on Monday, Deus said. The health bulletin said Rainier was still breathing with the aid of a respirator.

The palace has issued sparsely worded health bulletins nearly each day in the past week since Rainier, Europe's longest-serving monarch, was placed in intensive care March 22.

For the second straight day, Monday's bulletin lowered the apparent level of concern. On Saturday, his doctors said the prognosis was "extremely reserved," followed by "very reserved" on Sunday. Monday's bulletin said the prognosis was simply "reserved."

Rainier, who has suffered from bouts of sickness in recent years, was hospitalized at Monaco's Cardio-Thoracic Center on March 7 with a chest infection. He was transferred to the intensive care unit when his health took a sudden turn for the worse.

Rainier, who has ruled Monaco since 1949, is beloved in the principality, which is smaller than New York City's Central Park and larger than only one other independent state — Vatican City.

His family, the Grimaldis (search), has ruled Monaco for more than 700 years, but Rainier is credited with transforming it into a modern and elegant enclave known as a playground for the rich.

He married the American actress Grace Kelly (search) in 1956. She died in a 1982 car crash.

Rainier's son, Prince Albert, 47, is being groomed as a successor. Since Albert has no children, his sister, Princess Caroline, 48, would be next in line to the throne, followed by her eldest son, Andrea, now 20.