Sam Smith said they are "heartbroken" after their gig in Manchester was cancelled due to voice issues.
The 31-year-old singer, who surprised fans by saying they would be on stage with Madonna, was performing at the AO Arena on Wednesday night.
Smith was performing their "Gloria the Tour" to a packed out arena, but after four songs, the singer left the stage for some time.
Fans online said that there had been a power cut as the lights in the area were temporarily dimmed.
A while later, fans were told the show had ended due to "vocal issues" and were told to leave the arena.
Following the incident, Smith shared a statement on Instagram and apologised to fans.
"I don't know what to say honestly. I fought off a virus a few weeks ago and since then we have travelled across Europe and had such incredible shows.
"Today in soundcheck I felt fine and was so excited to give Manchester an amazing show tonight, with a special surprise guest at the end," they said.
The statement continued: "During my third song, I noticed something wrong with my voice. I prayed it was just my voice waking up for the show but into the fourth song I could feel something was really wrong.
"I came off stage and have tried everything to get my voice back in gear but it won't. I am honestly heartbroken I couldn't finish the show tonight for you all. I love you all. I'm sorry I'm sorry I'm sorry."
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Frustrated fans shared their views on Twitter to voice their disappointment.
One user wrote: "No idea what's gone on at the Sam Smith concert but if it genuinely is vocal issues I think they need to put out a statement asap. Not fair to cause so much unnecessary worry and anxiety with such a significant week in Manchester."
Another user said the situation could have caused many fans "anxiety" and could have been a "triggering" reminder of the Manchester Arena attack.
The attack, which occurred at an Ariana Grande concert on 22 May 2017, left 22 people dead - including children.
"If Sam Smith cancelled their show tonight due to their voice, surely they should have cancelled it BEFORE, seems insensitive to stop mid show, turn lights on and say there's issues at an arena where there was a serious terrorist attack, talk about anxiety for the crowd," they added.
The user continued: "I am not trying to start a riot against Sam as I am sure there was a good reason for the cancellation, but the anniversary of the attack was TWO days ago, so it's just very, very triggering to cancel a show with such immediate effect."
Sky News has contacted AO Arena for a comment.