Monaco's Prince Rainier has been moved into a hospital intensive care unit due to a lung infection he is being treated for has worsened.
The palace's press office said the 81-year-old monarch, who was married to late film icon Grace Kelly and rules the tiny state of Monaco on the French Riviera, had initially been responding well to treatment since his admission to hospital on March 7th.
The short statement did not make clear when Prince Rainier suffered the setback that prompted his transfer to the unit.
Prince Rainier, whose Grimaldi family has ruled the low-tax haven for seven centuries, has been in and out of hospital in recent years with both lung and coronary problems.
Born on May 31st, 1923, he has cut a lonely figure in recent years as media attention has shifted from him to the turbulent lives of his three children. Princess Grace, the radiant American actress he married in 1956, died in a car crash in 1982.
When Prince Rainier succeeded his grandfather Prince Louis II in 1949, Monaco was best known for the casino on which its early prosperity was founded in the 19th century.