Jessie J has caught a "severe stomach bug".

The singer was scheduled to perform at the Moon and Stars Festival in Switzerland tonight. However, she's had to pull out at the last minute after falling sick while travelling.

"I'm super sad to announce that I will have to cancel my show tonight- Moon and Stars Festival in Switzerland," she apologised to her fans on Twitter.

"Ive been touring Asia and have caught a severe stomach bug. I am so sorry to anyone who was coming to the show but I have been told by my doctor I must remain on bed rest until I recover... Awful timing! Can't believe it :( Look forward to seeing you all soon x (sic)"

The 26-year-old's fans were sympathetic, wishing her well and advising her to rest and drink water.

Stars who have taken to the stage at the Swiss festival this year, which runs July 10 to July 19, have included James Blunt, Dolly Parton and Jack Johnson.

The Backstreet Boys are set to perform tomorrow with British X Factor runner-up Rebecca Ferguson as a special guest.

Luckily Jessie has plenty to keep her feeling positive. She's collaborating with Nicki Minaj and Ariana Grande on single Bang Bang.

"Me + @arianagrande + @NICKIMINAJ = BANG BANG World Premiere 29th July!

#BangBang (sic)," she excitedly tweeted.