Friday is the culmination of a four-day celebration and the public was invited to the Stockholm palace courtyard to congratulate the 77-year-old king, the Nordic country's longest sitting monarch.

"I think it's important to honour our king, he has had 50 years on the throne today," Charlotta Gillersten, 59, a Stockholm resident, said as she and hundreds of others gathered at the palace. "I think he does a marvelous job for Sweden."

The Swedish king is the official head of state but is largely confined to ceremonial and representative duties.

Carl Gustaf ascended to the throne when he was 27 years old on Sept. 15, 1973, after the death of his grandfather Gustav VI Adolf. He was only nine months old when his father died in a plane crash.

Support in Sweden for the monarchy has risen and is at the highest level for 20 years, according to a survey by Gothenburg University published in May.

Almost half of Swedes have confidence or high confidence in how the monarchy conducts itself. Only 11% want to abolish the monarchy and turn Sweden into a republic.

The king, who suffers from dyslexia, was often ridiculed in the early years of his reign for misspeaking during speeches. But his popularity subsequently rose, in part thanks to an emotional and widely praised speech after the December 2004 earthquake and tsunami disaster in Southeast Asia in which more than 500 Swedish holidaymakers died.

He has also faced some scrutiny throughout the years. After a visit to Brunei in 2004 he was criticised for praising the "openness" in the country, a monarchy where the Sultan has absolute powers and full executive authority.

(Reporting by Johan Ahlander and Tom Little; editing by Mark Heinrich)