Demi Lovato's fans sing along after gig cancellation

Fans of the American singer, Demi Lovato performed a mass sing-along after the star postponed her gig at O2 in London due to illness.

Disappointed fans decided to try and cheer their favorite star with a song.

A fan tweeted, "MASS SING ALONG AT THIS SPIKE AT HALF 7 O2 ARE GOING TO TWEET IT TO DEMI @ddlovato @o2 come cheer yourselves up."

Another fan tweeted, "#o2demisingalong LOVATICS ORGANIZED A SING ALONG FOR U WE LOVE YOU."

"So this just happened outside the O2! I'm the one holding the 'O2' sign?? #O2DemiSingALong."

Lovato thanked her fans as she wrote, "My fans are seriously the best... I can't believe how much love and support I've received today.. the video of my fans singing skyscraper outside of the venue made me cry."

Earlier, Demi announced the news on Twitter, saying, "I have to postpone my concert in London at the O2 tonight due to being very sick and with swollen vocal chords that were examined by a doctor."

I am so sorry to disappoint any of my fans in London that have travelled hours to be here," she added.

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