Image caption Carrey (left) is "magnificent" in the film, according to Millar

Jim Carrey, star of Kick-Ass 2, has withdrawn support for the film following the Sandy Hook massacre.

Carrey tweeted on Sunday: "I did Kickass a month b4 Sandy Hook and now in all good conscience I cannot support that level of violence.

"My apologies to others involved with the film. I am not ashamed of it but recent events have caused a change in my heart," he added.

Carrey is well-known for his support of gun control measures.

Twenty pupils and six staff were killed at Sandy Hook Elementary School in Connecticut last December by 20-year-old gunman Adam Lanza. He had earlier shot dead his mother in their home.

'Passionate advocate'

Kick-Ass 2 follows 2010's ultra-violent comic book movie and sees Chloe Moretz and Aaron Taylor-Johnson reprise their roles as high school pupils turned DIY superheroes Hit Girl and Kick-Ass.

The movie will be released in the UK on 14 August and the US on 16 August.

Carrey's character in the film is Colonel Stars and Stripes, the leader of a group of superheroes.

Creator of the original comic book and Kick-Ass executive producer Mark Millar said he was "baffled" by Carrey's decision and asked him to reconsider.

In a forum on his website Millarworld, he wrote: "As you may know, Jim is a passionate advocate of gun-control and I respect both his politics and his opinion, but I'm baffled by this sudden announcement as nothing seen in this picture wasn't in the screenplay eighteen months ago.

"Yes, the body-count is very high, but a movie called Kick-Ass 2 really has to do what it says on the tin.

"A sequel to the picture that gave us Hit-Girl was always going to have some blood on the floor and this should have been no shock to a guy who enjoyed the first movie so much... like Jim, I'm horrified by real-life violence (even though I'm Scottish), but Kick-Ass 2 isn't a documentary."

Further down in his posting, he continued: "Ultimately, this is his decision, but I've never quite bought the notion that violence in fiction leads to violence in real-life any more than Harry Potter casting a spell creates more Boy Wizards in real life.,, Jim, I love ya and I hope you reconsider for all the above points."

Universal Pictures, the film's studio, has yet to comment on Carrey's decision.