Harald was on Tuesday admitted to the Sultanah Maliha hospital on the island of Langkawi, where he was on holiday, with an infection.

“The decision was taken this morning and the operation was carried out successfully,” the hospital said about fitting the pacemaker.

“The king is doing well but needs rest. The operation will make his return home safer,” explained his personal doctor, Bjorn Bendz.

The pacemaker is “temporary”, according to the entourage of the king, Europe’s oldest ruling monarch.

A medical plane operated by Scandinavian airline SAS landed in Langkawi on Friday but authorities did not confirm whether it was intended for the king, whose return home is being arranged by the Norwegian government.

Langkawi air traffic control told AFP that the SAS plane was not a scheduled flight and was due to depart on Sunday.

Harald, who turned 87 in February, needs crutches and has suffered a series of health issues in recent years.

He has had heart surgery and has suffered from respiratory problems.

In January, he caught a respiratory infection just a few 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.