A copy of X-Men Origins: Wolverine starring Hugh Jackman has been leaked online almost a month before its cinema release.

A high-quality work print has surfaced on BitTorrent and other internet file-sharing websites.

The copy is reportedly incomplete, without some of the special effects and additional scenes.

The leak comes almost a month before the movie's Australian and UK release on April 29, and the May 1 release date in the US.

Jackman and 20th Century Fox are due to unveil "world exclusive: finished footage from the film at a press conference in Sydney next week.

X-Men Origins: Wolverine sees Jackman return to the role of the clawed mutant and follows his quest for revenge after his girlfriend is murdered.

The film also stars Liev Schreiber, Ryan Reynolds and Will.i.am.

Fox said in a statement that the source of the leak would be prosecuted. It also said the FBI is investigating.