Europe’s oldest reigning monarch has been in hospital in Oslo since August 17, suffering from a blood disease.

The health of Norway’s 89-year-old King Harald, hospitalised with a blood disease, has deteriorated and he is in an “extremely serious” condition, the palace said.

Queen Sonja and Crown Prince Haakon, who is acting as regent during his father’s illness, have cancelled all royal engagements, the palace said in a statement on Thursday.

“His Majesty the King’s health condition is extremely serious,” it said, providing no other details.

Members of the king’s family were at his bedside, Norwegian media reported, with the queen, Haakon and his wife Mette-Marit seen arriving at the hospital.

Europe’s oldest reigning monarch has been in hospital in Oslo since August 17, suffering from haemolytic anaemia, a condition caused by an abnormally rapid destruction of red blood cells which leads to fatigue and shortness of breath.

The monarch was admitted to Oslo University Hospital due to fluid retention from the cortisone treatment he was receiving.

Harald, who ascended the Norwegian throne in 1991, has had multiple health problems in recent years, forcing him to have a pacemaker fitted and to scale back his official schedule.

But he has always ruled out abdicating, arguing that he took a lifelong oath before the Norwegian parliament.