In a statement, his family said he died of cancer and would be "hugely missed".

Kurtz worked with George Lucas on American Graffiti, the original Star Wars and its first sequel, The Empire Strikes Back. His other films included The Dark Crystal and Return to Oz.

Peter Mayhew - Chewbacca in Star Wars - remembered him as "a great filmmaker" who "touched the lives of millions".

Tribute was also paid by Elstree Studios in Hertfordshire, where the first Star Wars films were made.

Kurtz's family said he was "a magnificent man" whose "life's work was to share the wonder of audio-visual storytelling through the art of film."

"Gary was passionate about telling stories that shared the humanity of characters in entertaining ways for audiences around the world."

In its own tribute, special effects company Industrial Light and Magic (ILM) said he was "a key collaborator of George Lucas and a supremely talented storyteller".

Born in Los Angeles in 1940, Kurtz started out as an assistant director on Ride in the Whirlwind, a 1965 Western starring a pre-stardom Jack Nicholson.

After serving in the Marines in Vietnam, he began a collaboration with Lucas that saw him become an early champion of his nascent Star Wars saga.

His involvement extended to working as an uncredited assistant director on The Empire Strikes Back, whose title he conceived.

Yet his desire to work on other projects saw his partnership with Lucas dissolve and another producer take on Return of the Jedi, the next Star Wars film.

The Dark Crystal, a fantasy adventure featuring elaborate puppets, saw him work with Muppets creator Jim Henson. The 1982 film was Bafta-nominated for its special effects.

But his next films, 1985's Return to Oz and 1989's Slipstream, were not a success and led to him filing for bankruptcy.

In later life Kurtz made appearances in numerous documentaries about the Star Wars series, among them the BBC production The Galaxy Britain Built.

LucasFilm, producer of the Star Wars films, remembered him as "a man of immense talent and intelligence" who "leaves behind a powerful legacy in film."