King Harald V of Norway is in an “extremely serious” condition in hospital, the country’s royal household has said.

His wife, Queen Sonja, and his son, Crown Prince Haakon, have cancelled all royal engagements and they have gathered at his bedside at Oslo University Hospital with other members of the royal family.

The 89-year-old has been in hospital for over a week receiving treatment for a rare blood condition, haemolytic anaemia.

Having been on the throne since 1991, King Harald is Europe’s oldest head of state.

Crown Prince Haakon, 53, the successor to the Norwegian throne, has been serving as regent while his father is on leave.

King Harald has been treated in recent weeks with cortisone for haemolytic anaemia, a condition that causes the number of red blood cells in the body to be reduced, and leads to fatigue and shortness of breath.

Members of the royal family were seen arriving at the hospital on Thursday morning, including Haakon’s wife, Crown Princess Mette-Marit and her son Marius Borg Høiby.

King Harald’s sister, Princess Astrid is also at the hospital, according to reports in Norwegian media.

Prime Minister Jonas Gahr Støre has cancelled a planned trip to Germany, where he was expected to meet Chancellor Friedrich Merz on Thursday.

“The whole nation is with us as we send warm thoughts to the king and the rest of the royal family,” he said in a statement.

Members of the public have also begun laying flowers in Palace Square, in front of the palace in Oslo.