US singer Katy Perry during the photocall before the Chanel 2017-2018 Fall/Winter Haute Couture collection show in Paris, France, July 4, 2017. AFP/Patrick Kovarik/Files

CHICAGO: Pop star Katy Perry made a surprise appearance at an American couple's wedding over the weekend, taking photos and dancing with the newlyweds at their reception in St Louis.

Perry was in the midwestern city for a concert, when she and her entourage surprised newlyweds Hayley Rosenblum and Blonie Dudney at the Four Seasons Hotel on Saturday night.

"She actually asked the bride and groom if she could come in and crash their wedding, and they both said yes," Amy Prada ? a wedding guest ? told AFP.

"Everyone was shocked and happily surprised," Prada said, adding that Perry visited for about 15 minutes, dancing with the couple, and taking selfies with guests.

The surprise came late into the night.

Wedding photographer Ray Prop told St Louis Magazine that he was getting ready to leave.

"All of a sudden, the crazy human-train stopped right at the bride and groom, and a woman with short blonde hair in a baseball cap said: 'Do you mind if we crash your wedding?'," Prop said.

Perry was in town for her "Witness" tour, and mentioned the wedding visit during her Sunday performance, according to posts on social media.