Norway's King Harald, 83, taken to hospital
"The king is currently being examined," the palace said in a statement. "Covid-19 has already been ruled out."
The king, who has been on the throne for 29 years, is now on sick leave and Crown Prince Haakon will take over his duties temporarily.
He has insisted he will not abdicate despite declining health that saw him spend a week in hospital in January after a bout of dizziness.
In the early 2000s, he underwent surgery for bladder cancer and later to repair a heart valve.