The animated cartoon South Park is a cult hit

Trey Parker and Matt Stone are currently writing an untitled project, which they are expected to voice and direct, said trade paper Hollywood Reporter.

The film makers said earlier this year they were writing an animated movie, adding: "It won't have anything to do with South Park."

The project is to feature superheroes on a mission to eradicate "such things as terrorism" and "certain celebrities who have outworn their welcome in the public eye", according to the paper.

Parker and Stone are said to be making the film with producer Scott Rudin, whose films include Sister Act and The Addams Family.

The pair have built their career on controversial subject matter.

A South Park episode from 2001 saw Osama bin Laden being killed off, while former Iraqi leader Saddam Hussein was a previous target for their sense of humour.

The show has come under fire on occasion for its bad language, despite being aimed at an older audience, with critics saying it could influence younger viewers.