Peter Jackson is secretly working to adapt the Mortal Engines fantasy novels for the screen.

The hush-hush project is understood to be in early development, with work on the first of the four books under way, industry sources say.

Weta Workshops is also believed to be working on designs for the science fiction series, which features giant mobile cities.

A spokesman for Jackson did not deny the project was on the books yesterday, but said "any comment should come from Peter".

Jackson, who is understood to have had the rights to the books for some time, was unavailable for comment.

The books, by Philip Reeve, are set in a post-apocalyptic world where cities have become giant vehicles and must consume each other to survive. Mortal Engines is the first book in the series, and has won a Nestle Smarties Book Prize and was shortlisted for the 2002 Whitbread Award.

The fantasy books are the latest in a series of adaptation projects Jackson has taken on.

His film adaptation of The Lovely Bones premiered in Wellington last week, and he is producing The Hobbit – the prequel to his highly successful Lord of the Rings trilogy – and Steven Spielberg's version of the Belgian comic The Adventures of Tintin: The Secret of the Unicorn.

Jackson has also optioned the rights to the historic-fantasy Temeraire novels, which tell an alternative version of the Napoleonic Wars where tame dragons are used for aerial attacks.

World War II film Dambusters, which he produced and Kiwi film-maker Christian Rivers directed, is due for release next year.

Earlier this month Jackson also said he was contemplating making a World War I film about Gallipoli.

- The Dominion Post