Chinese directors Jia Zhangke and Tang Xiaobai say they have quit the biggest film festival in Australia because of personal beliefs - not because of any pressure from the Chinese government.

Their action was prompted by the planned airing of a documentary about Uygur separatist Rebiya Kadeer, who the Chinese government believes was behind the deadly ethnic riot in Urumqi on July 5.

The Melbourne International Film Festival starts today for a 17-day run.