Britney Spears
Britney Spears is in the midst of a two-year residency in Las Vegas, performing 200 showsEthan Miller/Getty

Britney Spears has been forced to cancel two of her forthcoming Las Vegas shows after falling on stage and injuring her ankle.

The 33-year-old pop star has been in the middle of performing her 1999 hit (You Drive Me) Crazy surrounded by back up dancers when she slipped and gripped her ankle in agony.

In the video published by TMZ, she is seen continuing the performance seated before she is helped to her feet. She can be heard telling the audience "sorry about that" before soldiering on for the rest of the set, albeit with a limp.

A statement to fans she confirmed that her doctor had "advised her not to perform Friday and Saturday evening so that she may heal." Both the 1 May and 2 May shows will be rescheduled.

The mother-of-two later took to social media that to break the bad news to fans and to reassure them that she was on the mend.

This is not the first time the singer has had an onstage mishap during her "Piece of Me" residency. In April her hair extensions fell out and back in December her sequined dress came undone.

The singer's two-year stint at Sin City's Planet Hollywood Resort & Casino is expected to wrap up at the end of 2015.

Meanwhile, Spears has announced that she is following in the footsteps of Kim Kardashian and Katy Perry by launching a mobile app.

The gaming app, which is a joint venture with Glu Mobile (the company behind Kardashian's game) will enable fans of the pop princess to "experience the glitz and glamour of the entertainment business".

Glu Mobile's chief executive Niccolo de Masi said: "People like Britney Spears obviously have been successful for more than a decade. They have brand recognition and social following everywhere: not just developed nations but also emerging markets."