The makers of a DVD of the hit 1978 Superman movie are facing a legal battle over bonus footage included in the release.

A UK company says film giant Warner Bros, who released the classic hit on DVD in 2001, included extra features like the actors' original screen tests and special effects test footage without permission.

Superman spawned four big movie versions

Pueblo Film Licensing says it gained the original production rights after the movie's producer, Alexander Salkind, died in 1997.

Superman, starring Christopher Reeve and Marlon Brando, was one of the most successful films ever at the time of its release, earning $300m (�200m) at worldwide box offices and spawning three sequels.

Payment

Pueblo Film Licensing says Warner Bros did not get permission to use some clips on the DVD, which also included previously unseen scenes and an audio commentary by director Richard Donner.

"You can't use the bonus material if you don't pay for it. That's the whole issue," said entertainment lawyer Jeffrey Spitz, who is representing Pueblo.

Pueblo filed the lawsuit in Los Angeles federal court on Monday, 24 June, and also have another lawsuit pending in California state court against Warner Bros over future Superman sequels.

Warner Bros acquired the rights to make future Superman sequels in 1993 - but has not done so.

Vintage

Their spokesperson said the studio had not seen the lawsuit but did not comment on pending litigation as a matter of policy.

Superman's DVD release came as many vintage films are put out on the format that has now gained wide popularity.

Its disc capacity means much more than just the film can be included - and most releases now come with bonus material such as out-takes and alternative endings.

Mr Spitz said the releases of classic movies on DVD could attract more legal problems.

"I wouldn't be surprised if this becomes a more heavily litigated matter," he said.

"It's clear that they [directors] weren't thinking about this when they made the classic movies."