OSLO -- Norway's King Olav V, the world's oldest reigning monarch, died here yesterday after suffering a heart attack. He was 86.

The king, who suffered a stroke in June, was a British-born Dane who became second monarch of modern Norway. His ancestry was firmly rooted among the bluebloods of Europe, but the Norwegians called him "Folkekongen" -- the People's King.

An only child, groomed for the throne from the time he was 2, he became a rallying point for his adopted countrymen during World War II, and as king, a beloved symbol of nationhood.

He had been the world's oldest reigning monarch since the death a year ago of Japan's Emperor Hirohito.

From his youth as a ski jumper and Olympic yachtsman to his elder years as Norway's representative on dozens of state visits, Olav maintained an unflagging pace.

He visited the United States and Britain last year and spent his 86th birthday sailing in an Oslo regatta aboard his 18-foot boat. This year, the 33rd of his reign, he stood for several hours on the palace balcony to receive Constitution Day tributes from a parade of citizens.

His love of the outdoors and sports was one cause of public affection for the king. During the 1973 oil crisis, Norwegians were enchanted by a photograph of the monarch carrying his skis on a crowded trolley, heeding government pleas to save gasoline and use public transportation.

He was born Prince Alexander Edward Christian Frederick on July 2, 1903, at Appleton House on the British royal estate of Sandringham in Norfolk, England, of a Danish prince and an English princess.

Parliament chose his father, Prince Carl, to stand for election in 1905 to the new throne when Norway's union with Sweden was dissolved. When he won, Carl took the name Haakon VII, and named his son, Olav. The names hark back to kings of Norway's rich Viking past.

Olav married his first cousin, Princess Martha of Sweden, on March 21, 1929, but liked to joke that he became so thoroughly Norwegian that his son and two daughters married Norwegian commoners.

In 1940, when Germany occupied Norway during World War II and the underground Council of State rejected Olav's request to stay behind to oversee the anti-Nazi resistance, Olav, his father and the government moved to England.

On the fifth anniversary of their departure, King Haakon returned to free Norway.

Haakon died in 1957, and Olaf became king. Olav's wife, Princess Martha, died in 1954, and he never remarried. They had three children, Princess Ragnhild Alexandra, Princess Astrid Maud Ingeborg, and Crown Prince Harald.