COPENHAGEN, Denmark (AP) — Norway’s 83-year-old King Harald V will be on sick leave for the rest of the week due to pain in his leg, the palace said Thursday.

The royal household in Oslo said the heir to the throne, Crown Prince Haakon, has stepped in and taken over his father’s duties.

Last year, the ageing monarch underwent a successful operation to replace a heart valve to improve his breathing. Doctors had ruled out COVID-19.

In 2005, the king’s aortic valve was replaced by an artificial heart valve. Such valves have a lifespan of between 10 and 15 years, the royal household said, adding it was “not uncommon” for such interventions to have to be repeated.

Harald is is Norway’s head of state, but his duties are ceremonial, and he holds no political power.

He ascended to the throne following the death of his father, King Olav, on Jan. 17, 1991.

The country’s first native-born king since the 14th century, he married a commoner as a prince and won hearts in his egalitarian country by leading the mourning in 2011 for the victims of mass killer Anders Behring Breivik.