Ari Aster is working on a ''nightmare comedy''.

The 'Midsommar' filmmaker revealed his latest project will be a slightly more lighthearted horror flick, and he teased the entitled movie will be over four hours long.

He told UC Santa Barbara's Associated Students Programme Board: ''All I know is that it's gonna be four hours long, [and rated] over 17 [years of age].''

The 33-year-old director added that it will be a ''zonky nightmare comedy'', although he is yet to reveal any details about the cast or when the project will begin production.

'Midsommar' terrified viewers when it was released last year, which follows a couple (Florence Pugh and Jack Reynor) who fall into a cult after travelling to Sweden for a festival.

Despite the movie's harrowing plot, Aster previously suggested that he saw it as a ''dark comedy'' and that the ending ''makes him laugh''.

He said: ''I've been calling this movie a wish-fulfilment film and fantasy from the beginning. It's a perverse wish-fulfilment film and fantasy.

''But for me, yeah, I do see the film as a dark comedy. The ending makes me laugh. Yeah, I was hoping to make kind of like a malignant crowd-pleaser.''

Aster added he wanted the film to make audiences ''question what they're feeling''.

He said: ''I'm hoping that 'Midsommar', especially, it's not just a movie that ends cathartically, but I'm hoping it's a film about catharsis in a way.

''I hope that whatever you're feeling at the end, whatever viewers feel at the end, I hope that they feel compelled to question what they're feeling and not just feel it. I also hope its funny, but I hope that the laughter catches in the throat.''

Will Poulter - who played Mark in the movie - said the movie was made even more ''disturbing'' because of a lack of the usual monsters seen in horror films.

The 27-year-old actor explained: ''What you come to terms with pretty quickly is that there aren't ghouls and goblins in 'Midsommar'.

''Everything that is horrifying comes from a very organic place and all the terrible things that happen are enacted by humans on humans. That's really quite disturbing to me.''