Jackman plays titular character Wolverine in the film
X-Men Origins star Hugh Jackman has called the leaking of his film a month before release a "serious crime".
An unfinished version of the film was downloaded an estimated 100,000 times from file-sharing websites last week and is now being investigated.
The Australian actor said it had left him "heartbroken" and amounted to a "Ferrari without a paint job".
He was promoting the Wolverine film at Cockatoo Island in Sydney Harbour and arrived by swooping from a helicopter.
The star unveiled 20 minutes of finished footage to around 600 fans at the location where much of the film was shot.
He said there would still be huge interest in its release later this month, despite the "upsetting" leak.
"There's no doubt it's very disappointing. Obviously people are seeing an unfinished film," Jackman added.
The star, who hosted the Oscars earlier this year, is embarking on a world tour to promote the film, which delves into the back story of his character Wolverine.
The illegal copy of the film is being looked into by the FBI, which could result in criminal proceedings.
The rough cut did not contain CGI special effects and frequently showed green screens and wires attached to actors.
A journalist for Fox News was dismissed earlier this week for posting a review of X-Men Origins based on a viewing of the illegal download.
Roger Friedman joked that he might watch other films using the same method.
The network condemned Mr Friedman's action as "reprehensible".