The Venice Film festival unveiled Hong Kong crime film Mad Detective as this year's competition surprise film entry on Wednesday night.

Co-directed by Hong Kong action film specialist Johnnie To and producer/director Wai Ka Fai, the film was presented Wednesday night at a press screening with no official pre-announcement but widespread speculation.

The only clue came in the form of a worn out paperback with the title Mad Detective on its cover: the film's press book.

Mad Detective is produced by To's production company Milkyway Image. Wai Ka Fai has collaborated on many projects with To since 1996. In addition to being creative director of Milkyway Image the two have directed and produced films together including Fulltime Killer (2003) and Running on Karma (2003).

To was last in Venice in 2006 with Exiled.

Mad Detective is about a rookie cop who teams up with a talented criminal profiler who is no longer on the police force but gets called back to solve a difficult crime involving a serial criminal with a multiple personality disorder.

But the rookie Inspector Ho starts to doubt the decision of calling in Bun due to his strange approach to crime solving.

Last year's surprise entry was Chinese director Jia Zhangke's Still Life, which went on to win Venice's Golden Lion and to be sold in more than 60 territories after its Venice win.

Also on Wednesday, Venice bestowed Golden Career Lion honours on director Tim Burton. Johnny Depp presented the award.

The ceremony also featured a sneak preview of Burton's upcoming film Sweeney Todd.

After the ceremony, The Nightmare Before Christmas was projected in 3D version. The original version was presented in Venice in 1994 while Burton's Corpse Bride was presented at the Venice Film Festival in 2005.

Marco Mueller, Venice's artistic director praised Tim Burton as 'a visionary.'

'This award will always inspire me to keep going,' Burton said. 'I have always loved Venice,' which he hailed as a festival whose focus is on 'the purity of loving movies.'

The festival wraps its 64th edition on Saturday.