Madonna collapsed twice on stage during a concert in Sofia, Bulgaria on Saturday, it's been reported.

Video footage of the performance appears to show the 51-year-old singer fainting onto one of her backing dancers during 'Holiday'.

According to the Sun newspaper, the star also collapsed as she left the stage following a rendition of 'Spanish Lesson'.

Madonna appears to fall ill during her performance of 'Holiday'.

A source claimed the star was “really worried backstage”, and had to “sit down for a longer break than usual between songs”.

The gig formed part of the second leg of Madonna's Sticky & Sweet world tour, which continued as scheduled last night in Israel.

Madonna live