20 carats of rubies and diamonds are woven into this bracelet

The pieces, including many of the diva's favourites - such as a ruby-strewn bracelet and huge pearl drop earrings - are being sold in Geneva.

Auction house Sotheby's believe the 11 items will fetch an estimated $1m (�539,000).

The collection includes items given to Maria Callas by her first husband, Giovanni Meneghini, half a century ago.

Callas, famed for her acclaimed role as Tosca in Franco Zeffirelli's stage production of the Puccini opera, married the Italian Meneghini in 1949.

Mystery

She later left him for Greek shipping magnate Aristotle Onassis. They shared a stormy relationship until he wed Jacqueline Kennedy in 1968.

Although the jewels' provenance is well-known, the identity of the seller is shrouded in mystery, says the BBC's Imogen Faulkes in Geneva.

In pictures: The collection

At the time of her death in 1977, Callas' multi-million dollar estate was the subject of much disagreement among her family and friends.

Now some of those who remember her are angry that her jewels are being sold off.

The film director Franco Zefferelli, for example, has described the sale as a shameful exploitation of the opera singer's legacy.

But Sotheby's Geneva director Brett O'Connor said it would allow her fans to own a piece of her memory.

"We wanted everybody to have a chance to have a piece of someone who was so liked," he said.