Norway has bid a final farewell to King Harald V in a state funeral attended by royalty and heads of state from across Europe and beyond, as tens of thousands of people lined the streets of Oslo to pay their respects.

The funeral procession set off from the Royal Palace along Oslo's main avenue to Oslo Cathedral, with a 21-gun salute ringing out from Akershus Fortress to mark the occasion. The king's coffin was carried on an artillery carriage, draped in Norway's red royal standard and topped with white flowers.

King Haakon VIII, who succeeded his father upon Harald's death, walked behind the coffin alongside other senior members of the royal family. Harald's widow, Queen Sonja, 89, and Haakon's wife, Queen Mette-Marit, who is recovering from a lung transplant performed in June, followed the cortege by car.

Harald V died on August 28 at the age of 89, after 35 years on the throne. He was Europe's oldest reigning monarch at the time of his death.

The church service at Oslo Cathedral was attended by an array of foreign dignitaries. Royals present included Britain's Prince William and Princess Anne, Spain's King Felipe VI and Queen Letizia, Sweden's royal family, Denmark's King Frederik and Queen Mary, the Netherlands' King Willem-Alexander and Queen Maxima, and Japan's Crown Prince Akishino. The monarchs of Belgium and Jordan were also among the guests.

Ukraine's President Volodymyr Zelenskyy and political leaders and dignitaries from more than 20 countries attended the service.

The speaker of Norway's parliament, Masud Gharahkhani, recalled a monarch who was "not afraid to meet his people with his rubber boots on." Prime Minister Jonas Gahr Støre said Harald "struck a balance between being stately and being down-to-earth. He made Norway greater. He spoke of a 'we' in Norway where everyone is there for each other."

Following the cathedral service, four F-35 fighter jets flew over the building, with one breaking away to symbolise the king's passing. The coffin was then carried to Akershus Fortress, where Harald was laid to rest in the royal crypt alongside his parents and grandparents in a private ceremony.

Flags were subsequently raised from half-mast to mark the conclusion of the private burial, bringing to a close 13 days of national mourning. Norway also observed a minute's silence as part of the day's ceremonies.

More than 46,000 people had filed past the king's coffin in the days preceding the funeral. Schoolchildren were permitted to miss classes to take part in the occasion.

Norwegian police described securing the funeral as the largest planned operation in the force's history.

The day was not without controversy. Marius Borg Høiby, the son of Queen Mette-Marit from a previous relationship, attended the funeral and served as a pallbearer during the transfer to the royal chapel. He is currently under house arrest and wearing an ankle monitor while appealing a conviction for rape and domestic violence.

Queen Mette-Marit has also faced heavy criticism, including from the prime minister, over her past association with the late US sex offender Jeffrey Epstein.

Despite the scandals surrounding the royal family, the monarchy remains broadly popular. According to a poll conducted for Norway's public broadcaster, 72 percent of Norwegians support the monarchy, while 20 percent favour a republic or another form of government.

King Haakon VIII, who became king immediately upon his father's death, last week swore an oath of allegiance to Norway's constitution before parliament. After the funeral, he and his family appeared on the balcony of the Royal Palace and waved to the thousands of people gathered outside.