Private letters revealing opera star Maria Callas' desire for revenge after she was jilted by billionaire Aristotle Onassis have sold at auction in Rome.

The letters fetched more than �4,000 at a Christie's auction on Wednesday, selling to a mystery bidder.

Eleven lots of the opera singer's letters and photographs sold for �13,000, much more than was expected before the sale.

I'm going to try to put a little order in my oh-so-painful head - I'll just try to survive these coming few months

Maria Callas

Telephone bids were made from Israel, the United States and France.

The sale of her effects had attracted much attention. It was thought her effects might go back to her home country of Greece.

Sent to her voice teacher Elvira De Hidalgo in the late 1960s, the letters unmask a bitterness against Onassis and Jacqueline Kennedy - the woman he was to marry.

Unfulfilled

Days after Onassis wed the widow of assassinated US President John F Kennedy in October 1969, Callas wrote: "It's cruel, it isn't true - both should pay and both will pay, you'll see."

Kennedy became known as Jackie O

Callas died alone, depressed and unfulfilled, in Paris in September 1977. She was 53.

Onassis, who had once given her a $1m diamond ring, died in March 1975.

Written as her nine-year affair with Onassis was collapsing, Callas' letters also touched on the disillusion she felt and her battle to lose weight.

She wrote: "I'm doing all right under the circumstances, but it's like I've been given a huge smack and I can't breathe any longer.

"I've received three telephone calls [from Onassis]. One I didn't take - the other two I did and it was a disaster.

"As I told you, he's lost it and that's something that's really horrible for me to accept.

The diva also struggled to keep her divine voice

"I'm in Paris and I'm going to try to put a little order in my oh-so-painful head. I'll just try to survive these coming few months."

Their affair continued after the marriage, but it was to prove the most humiliating period of Callas' tragic life.

As she struggled to hold on to her lover, the woman dubbed the "high priestess of opera" was also fighting to retain her voice.