Prince Rainier III's (search) chances of recovery from heart and kidney failure and respiratory problems were very slim, his palace said Friday, a day after his son and heir took over as regent of the Mediterranean principality.

Rainier remained in "precarious" health Friday and "hopes for a favorable outcome remain extremely weak," said a statement signed by a medical team of five doctors.

However, "in full agreement" with the 81-year-old monarch's three children, doctors considered "active therapy" justified for the time being.

It was the first time Rainier's three children, Prince Albert (search) -- heir to the throne -- and Princesses Caroline and Stephanie, have been mentioned in regular health updates.

Albert, 47, the only son of Rainier and his late wife, former actress Grace Kelly (search), took over Thursday as regent of this Mediterranean principality, in charge of all royal duties -- but not assuming the throne.

It is the first time since 1949 that Rainier, Europe's longest-serving living monarch, has not been in control of the Mediterranean realm famous as a playground for the rich and famous.

Monaco's royal powers were conferred on Albert after a royal commission, which had been appointed by Rainier, decided the elder monarch could no longer rule.

His father, who retains the throne, could regain the royal powers if he recovers.

Rainier was hospitalized March 7 and was moved to intensive care on March 22, when his health took a sudden turn for the worse. He was being treated for breathing, kidney and heart trouble.