Aug. 28 (UPI) — King Harald V of Norway died early Friday in an Oslo hospital where he was undergoing treatment for a rare blood disorder. He was 89 years old.

He passed peacefully at 6:35 a.m. local time, according to the Royal Palace, which said the royal flag was flying at half mast on the palace roof.

Family were called to his bedside after his condition worsened on Thursday at the national hospital, 10 days after he was admitted suffering from complications from haemolytic anaemia, a rare blood condition that depletes the number of red blood cells, causing fatigue and shortness of breath.

Harald leaves behind his wife Queen Sonja, also 89, the new king, Haakon, their daughter Princess Märtha Louise and six grandchildren.

King Haakon, 53, was due to hold an extraordinary council of state with the government later on Friday.

Harald’s cousin, King Charles, was among the first to pay their respects in a message in which he also wished Haakon, to whom he is godfather, “success and good fortune” as he assumes the monarchy.

In a statement on X, Charles and Queen Camilla said they were profoundly sad to hear his “dear cousin,” had died, extending their “deepest and most heartfelt condolences” to Queen Sonja and all her family, and saying Britain shared Norway’s grief at what he said was a time of “such heartbreaking loss.”

He said Britain and Norway shared a particularly close relationship dating back more than 120 years, with London one of the first capitals to recognize it following independence from Sweden in 1905 and that the allies’ bond was further strengthened by their shared “dreadful trials” during World War II.

Born in 1937, Harald’s mother brought him and his siblings to Sweden when the Nazis occupied Norway in 1940 and when U.S. President Franklin D. Roosevelt offered them refuge, moved to Washington for the remainder of the war, returning to Norway in 1945.

After becoming crown prince at the age of 20, Harald served in the military and went up to Oxford University in 1962 where he studied studied social science, history and economics at Balliol College.

He broke with royal tradition in the face of the opposition of his father, King Olav V, by marrying the then-Sonja Haraldsen, the daughter of a businessman, in 1968, instead of a scion of one the European royal families.

Harald stepped up as regent in 1990 after Olav became ill and ascended the throne in 1991 after his father died on Jan. 17 of that year.