Norway's King Harald has died at the age of 89 after a 35-year reign, with Crown Prince Haakon automatically succeeding to the throne.

King Harald, who had reigned since 1991, died on Friday at the age of 89, ending more than three decades on the throne. His 53-year-old son, Crown Prince Haakon, immediately became Norway's new monarch under the country's constitutional monarchy.

In a statement, the Norwegian Royal Palace said, "It is with deep sorrow that we announce the death of His Majesty King Harald."

The palace said the king died at 06:35 local time on Friday at Oslo University Hospital.

Public pays tribute

Flags at the Royal Palace in Oslo were lowered to half-mast as members of the public gathered for a second consecutive day to lay flowers and pay tribute to the monarch, who was widely regarded as a unifying figure in Norway.

Health had deteriorated

Europe's oldest reigning monarch had been receiving treatment for hemolytic anemia since Aug. 17. The condition causes red blood cells to be destroyed faster than they can be replaced.

The king's health deteriorated rapidly during the week, prompting the Royal Palace on Thursday to describe his condition as "extremely serious."

In recent years, Harald had faced recurring health problems, including undergoing pacemaker surgery, and had gradually reduced his public engagements.

Despite his declining health, he repeatedly rejected calls to abdicate, saying he had taken a lifelong oath before the Norwegian parliament.

Crown Prince Haakon becomes king

Under Norway's constitutional monarchy, Crown Prince Haakon automatically succeeded his father upon King Harald's death, ushering in a new chapter for the Norwegian royal family. (ILKHA)