Prince Rainier’s son, Albert, has assumed the royal duties of his ailing father.
Monaco’s Crown Council says as Prince Rainier is no longer able to carry out his sovereign functions.
However, a brief statement from the Palace did not say whether Prince Albert, who is in line to succeed his father, was taking over the monarch’s duties permanently.
The 81-year-old has been in hospital for three weeks after suffering lung, heart and kidney problems.
Prince Albert is the only son of Prince Rainier and his late wife, the American actress Grace Kelly.
His father has been in intensive care since early last month. The palace says he stabilised after three sessions of kidney dialysis but his condition is described as “very fragile.”