Stockholm, Sweden | "Mamma mia"! The four members of Swedish 1970s pop phenomenon ABBA were reunited in Stockholm , but sadly for fans only for the opening of a restaurant.

Questioned by reporters Benny Andersson, the one on the piano, insisted that he didn't think the four of them would be getting back together on stage.

"We are here to party," said his co-composer Bjorn Ulvaeus, the one on the guitar.

Together with singers Agnetha Faltskog, the one with the long blond hair, and Anni-Frid Lyngstad, the brunette, they formed Abba, the pop group which took the world by storm in the 1970s and early 1980s with hits such as "Waterloo" and "Dancing Queen".

The famous quartet who were once married to each other hadn't been seen out together since 2008. On Friday they arrived and left separately and wouldn't be photographed together.  

Abba have sold more than 380 million album worldwide since their breakthrough at the 1974 Eurovision Song Contest.