Norway's King Harald, Europe's oldest living monarch, has died at 89, the royal court said on Friday.

The monarch had been receiving treatment for a rare blood condition, hemolytic anemia, at Oslo University Hospital since mid-August.

His son, Prince Haakon automatically becomes King Haakon VIII, with the Norwegian Royal Court also confirming on Thursday that his wife, Mette-Marit, will become queen.

The Norwegian monarch is head of state, but has a largely ceremonial and representative role.

What the palace said about King Harald's death

"It is with deep sadness that we announce that His Majesty King Harald passed away today. King Harald passed away peacefully at Oslo University Hospital on Friday, August 28 at 6:35 a.m.," the palace said in a statement.

Harald's condition worsened over the last few days, and his wife, Queen Sonja, and son, Haakon, canceled all their engagements to be at his bedside.

Harald, who had been king since 1991, suffered a series of health problems in recent years and had increasingly scaled back his official duties. However, he repeatedly ruled out abdicating, saying the oath he had taken on becoming king "lasts for life."

Hundreds of well-wishers gathered outside the royal palace in Oslo overnight, holding a vigil as the king's condition deteriorated.

World leaders, royals pay tribute 

Britain's King Charles expressed his condolences for Harald's death, paying tribute to a "towering figure" who guided his country with "warmth and humility."

Norway's prime minister, Jonas Gahr Stoere, said Harald demonstrated an "unwavering faith in the Norwegian people" and "helped us to see the best in ourselves – and in one another."

Swedish King Carl XVI Gustaf said the late king had "been a good friend" and would be "mourned by many in our country."

"I wish my dear Godson Haakon, who now succeeds his father as head of state, success and good fortune in the important role that lies ahead of ‌him," he added.

King Frederik and Queen Mary of Denmark praised Harald's "warm personality and rock-solid calm," saying he "combined duty and responsibility with presence and humanity. He was loved like few others and will be missed by many."

European Commission President Ursula von der Leyen described him as "a true European and a lifelong servant of his people."

"In moments of joy and sorrow, he brought Norwegians together," she said.

NATO chief Mark Rutte said Harald "showed himself to be a dedicated leader. His own military roots made him a champion of the Norwegian military and a long-time friend of NATO."

How will King Harald be remembered?

Born in 1937, Harald became Norway's first prince to be born in the country in more than 500 years. As a child, he fled Norway with his mother and sisters following the Nazi invasion in 1940, spending much of World War II in the United States.

Harald succeeded his father, King Olav V, in January 1991 and went on to modernize the Norwegian monarchy during more than 35 years on the throne. He was widely praised for his response to the 2011 far-right terrorist attacks that killed 77 people and later drew attention for speeches stressing tolerance, diversity and LGBTQ+ equality.

The king's death comes after a turbulent period for Norway's royal family.

King Harald V waves during a 1991 coronation tour after his accession to the throneImage: Lise Åserud/NTB/picture alliance

Crown Princess [nonw Queen] Mette-Marit has faced scrutiny over her past correspondence with the late US sex offender Jeffrey Epstein. Her son from a previous relationship, Marius Borg Hoiby, was sentenced in June to four years in prison after being convicted of two rapes and dozens of other offenses, including violence against a former partner. He has appealed the verdict.