Madonna has apologised for posting online photos of civil rights campaigners Martin Luther King, Jr. and Nelson Mandela showing them apparently bound with black wire.

In a bid to promote her upcoming release Rebel Heart the singer posted a photo of the album cover on Instagram.com, showing an image of her tied up.

However, she then risked controversy by adding edited images of Mandela and Luther King, Jr. with the same black wire apparently tired around them.

Madonna quickly came under fire for the photos, with critics accusing her of comparing herself to the historic civil rights campaigners and using them to market her music.

On Saturday (03Jan15), Madonna release a statement on her Facebook.com page to apologise, writing, "I'm sorry. I'm not comparing my self to anyone. I'm admiring and acknowledging there (sic) Rebel Hearts. This is niether (sic) a crime or an insult or racist! I also did it with Michael jaclson (sic) and frida khalo (sic) and marilyn monroe. Am I say (sic) I am them, NO. I'm saying they are Rebel Hearts too. And I didn't do it, my fans did. And I just re-posted those photos. My fans aren't racist either. If they put me in the same category as those other people, Thank you. I'm very flattered and I hope one day to live up to 1 100th of what those people accomplished."