Unreleased Michael Jackson songs have been stolen by hackers.

Record company Sony music say over 50,000 tracks - including never before heard material the late singer had recorded with will.i.am and Freddie Mercury - were stolen in the attack, thought to be the largest of its kind on a record company.

A source told The Sunday Times newspaper: ''Everything Sony purchased from the Michael Jackson estate was compromised.

''It caused them to check their systems and they found the breach. There was a degree of sophistication. Sony identified the weakness and plugged the gap.''

Sony bought the rights to sell Michael's back catalogue in 2010 - a year after he died from acute Propofol intoxication - in a $250 million deal, which also allows them to release up to 10 new albums, including unreleased recordings.

Two men appeared in court in the UK on Friday (02.03.12) accused of offences in connection with the alleged security breach.

James Marks, 26, and James McCormick, 25, denied charges under the Computer Misuse Act and the Copyright, Designs and Patents Act and were bailed. They are due to stand trial next January.

Black Eyed Peas star will.i.am worked on at least three tracks with Michael, 'Dreaming', 'Still the King' and 'I Will Miss You', but has said he didn't want to release them as they were not finished and Michael would not have approved.

He said: ''Michael Jackson songs are finished when Michael says they're finished. Maybe if I never worked with him I wouldn't have this perspective. But he was very particular.''