Bollywood star Hrithik Roshan has branded his marriage split and brain surgery the "toughest challenge" he has ever faced.

The actor endured a miserable 2013, undergoing an operation in Mumbai, India to remove a blood clot in his head, and just five months later he announced his wife Sussanne Khan had left him after 13 years of marriage.

Now Roshan has spoken out about his year of hell, insisting he is stronger for the experience and dealt with his heartache by channelling his emotions into his new movie role as a lovestruck spy in Bang Bang.

He tells the Hindustan Times, "In a way (it was difficult)... But it has been very enlightening too. It has also been very easy because once you overcome the toughest challenge, the rest of the things become really simple. It has actually been quite simple and easy...

"(The film) was more challenging due to emotional reasons. But that is exactly where the mental strength comes in. This is the brightest film I have done. And I'm playing a happy character. I did all this at a time when my life was in deep contrast to that."