She famously becomes her alter ego Sasha Fierce when she performs. But fans saw another side of Beyoncé after an overzealous fan stepped out of line during a concert.

The 31-year-old singer reprimanded the male admirer after he slapped her on the backside during her show in Denmark.

The star, who is on the European leg of her Mrs Carter Show world tour, was performing her track Irreplaceable at the Forum Copenhagen.

In a video posted online, Queen B can be seen wowing the crowd as she struts on the catwalk in her blue catsuit.

After handing her microphone to various fans to sing along she turns to go back to the main stage when the unidentified fan stretches out his arm to slap her behind.

As the crowd gasps at his antics, the distinctly unimpressed performer can be seen quickly turning around and threatening to have him thrown out of the concert.

Looking directly at him Beyoncé can be heard fuming: "I will have you escorted out right now, alright?"

Ever the professional, the Single Ladies hitmaker shrugged off the frisky behaviour and continues singing.

The star, who is married to rapper Jay-Z is due to perform in Stockholm, Sweden, on Tuesday night (28 May).