Madonna's final Sticky & Sweet concerts in Israel were thrown into doubt on Saturday - after she collapsed on stage during a show.

The star was performing in the Bulgarian city of Sofia when she passed out mid-way through the set. Footage from the concert shows she was caught by one of her dancers who held her up and made sure she was okay to continue.

The 50-year-old singer refused to halt the gig and continued her rendition of Holiday, before reportedly walking off stage during her track Spanish Lesson after falling ill again.

A source tells British newspaper The Sun, "Madonna was really worried backstage. She had to sit down for a longer break than usual between songs. She refused to end the show after the Holiday dizzy spell. It turns out she is suffering from exhaustion. She is anemic."

The publication reports that after being checked over by doctors after the Sofia show, the star was advised to scrap her final two shows in Israel. The insider adds, "She was advised to postpone the last two shows for a few days, but logistics and stubbornness stopped her. She'll do them and then take a rest."

Madonna took to the stage in the Israeli capital Tel Aviv as scheduled on Tuesday night.

Update: we got hold of the video, and it appears it was part of Madonna's dance routine:

Image ©PR Photos

(This news article provided by World Entertainment News Network)