The legendary four-piece, who last sung together on Swedish television in 1986, reunited at a party in Stockholm, Sweden, to celebrate the 50th anniversary of members Björn Ulvaeus and Benny Andersson becoming friends.

According to editors at Swedish newspaper Expressen, Benny and Bjorn were joined by bandmates Agnetha Fältskog and Anni-Frid Lyngstad (Frida) on stage at the event, held at the city's Berns Hotel and nightclub.

All four members reportedly then performed The Way Old Friends Do, which appeared on their 1980 album Super Trouper.

Speaking to the publication about the celebration, Frida said, "It was absolutely amazing. A lot of emotions. We've made this journey throughout our history. Benny and Bjorn in particular. Its been very nostalgic."

After winning the 1974 Eurovision Song Contest for Sweden with the song Waterloo, the group enjoyed spectacular commercial success around the world with hits like Knowing Me, Knowing You, Money, Money, Money and Dancing Queen.

The band stopped touring and recording in December 1982 but returned in 1986 for a one-off performance on Swedish TV to honour their manager Stig Anderson.

Before briefly reuniting in January this year (16) to help Bjorn launch a restaurant in Stockholm, all four members of the band had not been seen in public together since 2008, when they hit the red carpet at the London and Stockholm premieres of the film version of the musical based on their songs, Mamma Mia!