Christian Bale was in Beijing on Monday to promote a movie about 13 young prostitutes set during Japanese army's brutal rampaging of China's wartime capital, known in the West as the Rape of Nanking.

The Oscar-winner and Batman star plays an American man in the film The Flowers of War, directed by one of China's best known modern directors, Zhang Yimou.

It is an adaptation of a Chinese-language novel by contemporary writer Yan Geling about 13 sex workers in Nanjing who volunteer to replace university students as escorts for invading Japanese soldiers. In the novel that translates roughly as The 13 Women of Nanjing, the American man leads a church that shelters prostitutes and young female students during the invasion.

Historians say the 1937 massacre in the eastern city now known as Nanjing resulted in the slaughter of at least 150,000 civilians. China puts the number killed at 300,000, making it one of the worst atrocities of the Second World War era.

Bale praised the ability of the actresses who play the young students in the movie to act fearful and upset for extended periods of time.

"Poor girls, they were always crying their eyes out," the actor said. "When I first arrived, I felt: this is just not good. I don't like that —the girls having to be upset for 10 hours a day. They were crying their eyes out for 10 hours a day, I don't know about you but for me it was exhausting — it makes you ill.

"But they were actually really good actresses because they could suddenly stop and kind of go 'hahaha, we can be like that' and I was so happy to see that."

Director Zhang said he wanted to show the "brilliance of humanity in a circumstance of war" through the dramatic story.

"I think as long as the story is moving people from all over the world will like it," said Zhang, whose credits include A Simple Noodle Story, an adaptation of the Coen brothers' 1984 movie Blood Simple, the love story Under the Hawthorn Tree, praised early works like Raise the Red Lantern and in his martial arts films like Hero and House of Flying Daggers.

The film hits Chinese screens on Friday.