The composer behind Chris Hemsworth's new movie Blackhat has blasted Michael Mann over suggestions the director "sliced and diced" his score.

Harry Gregson-Williams headed to a screening of the action thriller last week (ends11Jan15) and was shocked to realise the 90-minute score he had created for the film was barely used and was replaced by music he did not recognise.

Gregson-Williams took to Facebook.com to explain the situation to fans, writing, "I would like it to be known for what it's worth that the 'score' for Blackhat maybe credited to me, but contains almost none of my compositions. I attended the premiere of the movie at the end of last week and discovered, to my horror, music that shocked and surprised me... quasi emotional (synth) string pieces that I'd never heard in my life before...

"I can say nothing for certain except that I was not the author of most of what is now in the movie. I feel like I want to point this out... as my name is right there listed as the lead composer and one would expect that credit to mean something, but it doesn't...

"I therefore reluctantly join the long list of composers who have had their scores sliced and diced mercilessly or ignored completely by Michael Mann..."

The post has since been deleted.

The film, about U.S. and Chinese agencies which team up with a convict to track down a cyber criminal, is released in the U.S. this week (ends16Jan15).