STOCKHOLM (AFP) - Mamma mia! The four members of Swedish 1970s pop phenomenon Abba were reunited in Stockholm on Wednesday, but sadly for fans only for the opening of a restaurant.

Their rare reunion was for the opening of fellow member Bjoern Ulvaeus' Greek taverna-style restaurant, called Mamma Mia! The Party and inspired by the Mamma Mia! musical and movie.

Benny Andersson, with singers Agnetha Faltskog and Anni-Frid Lyngstad, also showed at the restaurant, where guests are invited to sing along to Abba tunes, reported The Telegraph.

The restaurant is housed in Stockholm's Tyrol restaurant and based on the Greek taverna in the Mamma Mia! musical.

Questioned by reporters, Andersson, who is the Abba member on the piano, insisted that he did not think the four of them would be getting back together on stage.

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

Together with Faltskog, the one with the long blond hair, and 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, Dancing Queen and Mamma Mia.

The famous quartet who were once married to each other had not been seen out together since 2008.

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