Sweden's king on Friday handed royal orders to the members of iconic pop group ABBA, marking the first time in 50 years the honours have been awarded in the Nordic country.

At a ceremony at the royal palace in Stockholm, King Carl XVI Gustaf presented the Royal Order of Vasa to Benny Andersson, Agnetha Faltskog, Anni-Frid Reuss and Bjorn Ulvaeus, who made a rare public appearance together.

Known for disco hits like "Mamma Mia" (1975), "Dancing Queen" (1976), and "The Winner Takes It All" (1980), the four were honoured for "outstanding achievements in Swedish and international music."

Sweden stopped awarding royal orders to its own citizens in 1975, as the practice was deemed anachronistic.

The country continued to award royal orders to foreign citizens.

However, the country's parliament reinstated the practice in 2022 and Friday's ceremony marked the first time the orders were awarded to Swedes in half a century.

This year also marks the 50th anniversary of ABBA's 1974 Eurovision Song Contest win with "Waterloo", which launched the group's international breakthrough.

With their unique style and catchy melodies, the group personified disco around the globe until they stopped performing in 1982.

ABBA's popularity was rekindled by the "Mamma Mia" films, which introduced the group's music to new generations.

The quartet has also returned to the stage through ABBA Voyage, a new album released in 2021, and a permanent show of the same name in London in which they are represented by digital avatars (holograms).

In total, 13 Swedes were honoured for their achievements at the ceremony, including two Nobel Prize winners: geneticist Svante Paabo and French-Swedish physicist Anne L'Huillier.