Aamir Khan, who has played a variety of roles in his 25-year-old career, says 'Dhoom 3' is his toughest role so far

In the last couple of years, the 48-year-old star gave hits in the form of 'Taare Zameen Par', 'Ghajini' and '3 Idiots' and his role in each of them was as different as chalk to cheese.

But he said: 'I think 'Dhoom 3' is my toughest role so far. I have never played anything like this before.' 'Every film is challenging, but this was a tough role. I had a great time working in the film,' Aamir told reporters Wednesday at the trailer launch of the film. In terms of preparation, the actor had to workout a lot for 'Dhoom 3'. 'I am playing a gymnast in the film. I also went for circus training for the film. There was a lot of hard work for the film. I followed a strict diet.'

The actor plays a negative role in director Vijay Krishna Acharya's sleek and stylish thriller -- but says not to compare it with the typical villain of the big screen. 'I liked the story and I was amazed after reading the script. I am not playing a typical Hindi cinema villain in 'Dhoom 3'. I don't want people to feel I am playing a villain,' said Aamir.

Abhishek Bachchan, his co-star in the film, was also present at the event. ''Dhoom 3' is much more edgier. I wouldn't call Aamir villain of the film,' said Abhishek who featured in the earlier two parts of 'Dhoom' that started in 2004. Also featuring Katrina Kaif and Uday Chopra, the film will come out Dec 20.