Michael Bay has confirmed he will not return for 'Transformers 5'.

The director has enjoyed a huge amount of success with the 'Transformers' franchise - with the latest film, 'Transformers: Age Of Extinction', grossing more than $1 billion worldwide - but Bay says he wants to try his hand at other challenges.

The 49-year-old told USA Today: ''There's kind of a new chapter, a new direction in movies I want to make.

''I have a lot of stories to tell. And it's about flexing new muscles.''

Bay has been working frenetically over the last few months, with another of his movies, 'The Purge: Anarchy', hitting cinema screens this summer.

And the director admits he's surprised to have come through such a heavy work schedule so well.

He said: ''I gotta tell you, it's been a crazy year with all of this stuff. I have no idea how we got through it all.''

Despite this, Bay is already looking forward to new projects, with the 'Teenage Mutant Ninja Turtles' among the most exciting movies on his horizon.

Paramount Pictures announced plans to make a sequel following early success at the box office with the current flick, which features Megan Fox, Will Arnett and William Fichtner.