The Babadook director Jennifer Kent has defended her new film The Nightingale as an “honest and necessary depiction” of a brutal historical moment, after rape scenes and graphic violence caused some ticket holders to walk out of screenings on Sunday and Monday night.

The film, written and directed by Kent, is set in 1825 Tasmania during the frontier war massacres of Indigenous Australians. It is framed around the story of Claire (Aisling Fanciosi), a 21-year-old Irish former convict who finds herself trapped by a brutal master, Lieutenant Hawkins (Sam Claflin).

Within the first half hour, Claire is held down and raped multiple times by multiple people, with camera framing that forces the viewer to watch the pain in her face – almost from the vantage point of her rapist. According to one report, audience members at the film’s Sunday night screening in Randwick walked out of the cinema, with one woman shouting, “She’s already been raped, we don’t need to see it again.”

The final time Claire is raped, her husband and baby are murdered in the same room, in a scene punctured by loud shouts from the Monday night audience. She then pays a local Indigenous man, Billy (Baykali Ganambarr), a shilling to guide her to Launceston, where she hopes to have her revenge.

As Claire and Billy take off on the journey that will bring them closer together, the audience bears witness to more pointblank murders by the English invaders, particularly of Indigenous people, one of whom – a woman with a toddler – had been taken as a sex slave.

Speaking to the audience on Monday night, after a screening from which a handful more audience members walked out, Kent said she understood that the rape scenes would be difficult to watch, as they had been difficult to make – but that she believed they had not been shot in a distasteful way.

By focusing on the faces of the women rather than their bodies, she said, she wanted audiences to reckon with the pain and trauma of female convicts from the era. These women were outnumbered eight to one and suffered so much at the hands of their masters – rape, beatings and psychological abuse – that they would deliberately commit small crimes, just to be locked up in solitary confinement for three weeks at a time.

In a comment released to media on Monday, Kent said both she and Franciosi had been contacted by victims of sexual violence who were grateful for the movie. “I do not believe this would be happening if the film was at all gratuitous or exploitative,” she said.

“Whilst The Nightingale contains historically accurate depictions of colonial violence and racism towards our Indigenous people, the film is not ‘about’ violence … We’ve made this film in collaboration with Tasmanian Aboriginal elders, and they feel it’s an honest and necessary depiction of their history and a story that needs to be told. I remain enormously proud of the film.”

Jim Everett, a Tasmanian Indigenous elder who was brought in on the treatment and worked on the film through to post-production, is an executive producer. “You rarely see the truth being told even in documentaries about what happened in Tasmania, that there was a definite attempt at genocide,” he says in the film’s production notes. “I felt that as a fiction it reflected real history, and so I should give it my support.”

In fact, Kent said, when it came to colonial violence against Indigenous Australians in Tasmania, the film actually held back. “If we showed what really happened in Tasmania in 1825, no audience could bear it.”

The Nightingale is the first full-length film to feature Palawa Kani, a reconstructed dialect drawn from the near-extinct Indigenous Tasmanian language, which Kent said developed further as her movie was made.

The movie premiered at Venice film festival last year, where it was the only female-led film in the main competition, and where it won the special jury prize.

When asked on Monday what she expected people to walk out of the cinema feeling, Kent said: “I try not to have expectations. I never expected the Babadook to become a gay icon. But it’s 2019, and here we are.”