King Harald of Norway was returning home from Malaysia on Sunday after falling ill on holiday and spending several days in hospital, the royal palace said.
The oldest reigning monarch in Europe at 87 years old, Harald contracted an infection on a trip to the island of Langkawi and was admitted to hospital on Tuesday.
The palace said on Saturday that he had been fitted with a “temporary” pacemaker, which his personal physician said would make his return safer.
The palace said in a statement on Sunday that Harald would “soon be on his way to Langkawi Airport for medical transportation”, and would be joined by Queen Sonja.
“Upon arrival in Norway, His Majesty will be admitted to the hospital Rikshospitalet” in Oslo, the statement continued.
“His Majesty will be on sick leave for two weeks.”
A medical plane believed to be transporting the king took off from Langkawi on Sunday afternoon, after police escorted a convoy that included an ambulance from the hospital to the airport, an AFP journalist saw.
Langkawi air traffic control earlier told AFP that a medical plane operated by Scandinavian airline SAS was due to depart on Sunday.
The flight is due to land in Oslo at 2259 GMT, according to specialist website Flightradar.
Harald needs crutches to get around and has suffered a series of health issues in recent years.
He caught a respiratory infection in January, days after dismissing speculation that he might abdicate, following the lead of distant cousin Queen Margrethe II in Denmark.
In his absence, Crown Prince Haakon, 50, has stepped in as regent.
