US actor Leonardo DiCaprio gives a speech at the start of the 11th Hour auction at Christie's in New York.

Johannesburg - Star actor Leonardo diCaprio has unleashed a pack of lawyers on American memorabilia dealer, Gary Zimet, in an attempt to retrieve a signed photograph of icon Nelson Mandela which he claims belongs to him, the Sunday Times reported.

Zimet kept the photograph in a vault but took it out this week to pose for the Sunday Times.

The colour image, taken while DiCaprio was filming the 2006 movie Blood Diamond, was put out for auction on Zimet's online auction house, Moments in Times, earlier this month.

Mandela personally wrote on the image: “To Leo DiCaprio, Best Wishes, Mandela, 4-8-07.”

But for some reason the photograph never reached the actor.

The Nelson Mandela Foundation said it was unaware of the picture's existence.

Danielle Melville, speaking on behalf of the foundation, said :”We are not aware of this image, nor do we have a record of it on our archive, so we are unable to comment.”

Zimet has already received offers of more than US25 000 (about R264 000) for the portrait which measures 23 x 30cm.

On learning of the picture's existence, DiCaprio's publicist and attorney Steve Warren said it belonged to his client who was demanding it back.