Bryan Singer claims 'X-Men: Days Of Future Past' will be ''darker'' than previous films in the series.

The director has shot the second prequel to the original X-Men trilogy, and claims while it retains some jokes, the storyline - which includes a dystopian future where all the mutant heroes are locked in internment camps - is no laughing matter.

He said in a Twitter chat: ''Though there is a great deal of humour, the overall tone is a bit darker than previous films, particularly because of the stakes...''

Details of the exact plot remain scarce, but as far as the characters to be included, he added Mystique (Jennifer Lawrence) will be ''a much more hardened, kick-ass character than she was in [previous prequel] 'X-Men First Class'.''

Singer also said new mutants in the film include Blink, Bishop, Sunspot, Warpath, Ink and Quicksilver.

Reprising their roles in the movie are Michael Fassbender as Magneto, James McAvoy as Professor X and Jason Flemyng as Azazel.

Singer stepped in to direct 'Days Of Future Past' after 'First Class' director Matthew Vaughn stepped down, but is no stranger to Marvel's X-Men franchise, as he has worked with it from the beginning, directing the original 'X-Men' in 2000 and 'X2' in 2003.

He added: ''I was real comfortable with the original cast and knew the #FirstClass cast as a writer/producer but not yet as a director. With the exception of @NicholasHoult [Beast] of course - but they were all fantastic and made the experience fun.''