Aaron Kwok stars the upcoming crime thriller Peace Keeper. [Photo provided to China Daily]

From the 2005 hit Divergence to the 2015 award-winning crime thriller Port of Call, Hong Kong star Aaron Kwok has portrayed a number of impressive looking policemen on big screen.

But in the upcoming action thriller Peace Keeper, Kwok says his incarnation of a morally-tainted officer is difficult and challenging.

The film, also starring Wang Qianyuan, a best-actor winner at the 23rd Tokyo International Film Festival, will open across China on Aug 17.

The cast includes Liu Tao, a veteran actress from the hit TV series Ode to Joy.