When Kaouther Ben Hania heard Hind Rajab’s voice for the first time, she was in Los Angeles airport scrolling through social media. The five-year-old’s cry for help cut through the clamour around her. This was in February 2024 and Hind had already been dead for at least a week, left to bleed out among the corpses of six of her relatives after their car was targeted by an Israeli tank, leaving it with 335 bullet holes, according to the Forensic Architecture research group.

More than 20,000 Palestinian children were killed in two years of Israeli bombardment of Gaza, according to UN estimates. Another 82 have been killed since 10 October when a ceasefire was declared and then routinely breached. The pictures of the dead have often been published online, including those of Hind, showing her dressed in pink with a floral tiara, or smiling in an oversized academic cap and gown, but her voice also remains to haunt the world after her death.

The Palestine Red Crescent Society (PRCS) posted audio recordings of her last hours, made by the organisation’s emergency call centre via a mobile phone in the car, as Hind repeatedly, desperately, appealed for someone to rescue her. On the same recording, we can hear the increasingly fraught workers at the centre promising her that help would soon be on the way.

When Ben Hania heard Hind’s voice, it brought her to an abrupt halt in the airport terminal, as travellers milled around her. This was a young child calling on adults to protect her amid the appeal of Palestine to be saved from genocide – and on both counts, the world had failed. “When I heard her voice, for that millisecond, it felt as if she was asking me to save her,” she says. “There was something very immediate in her voice, and it was very shocking.”

The Tunisian director was between stops on a US tour promoting her latest film, having already begun work on her next. But she immediately cleared her calendar so she could start a new film based around Hind’s voice. “It was in my head for days and days,” says Ben Hania. “I felt a very strong sense of sadness and helplessness. I was wondering, ‘What can I do?’ The only thing I know how to do is make movies.”

The outline of the film began to take shape as Ben Hania researched the circumstances of the recording. She found out that the clips the PRCS had put online were just fragments. They had recorded the whole call, lasting three hours, and they sent it all to Ben Hania. Listening to all of it, knowing how it would end, was “one of the most difficult things I’ve heard in my life”, she says.

There was one last thing to be done before starting work – calling Hind’s mother, Wissam Hamada, who was in mourning in Gaza. “I told her, ‘I want to do a movie. Tell me if you don’t want me to and I won’t do it. And she told me, ‘I don’t want my daughter to be forgotten. I want justice for my daughter. So if this movie can help, do it please.’ So it started.”

The result, called simply The Voice of Hind Rajab, is a dramatic recreation of the tragedy as it unfurled in the narrow confines of the Red Crescent call centre, with actors playing the roles of the four emergency workers who were on the other end of the line – but Hind’s voice is her own. The actors respond to the real voice, trying to encourage and console Hind as the emergency workers had done, recreating the agony of their ultimate failure.

Many films contain images that cannot be unseen. The Voice of Hind Rajab cannot be unheard. Ben Hania succeeded in the task that Hamada entrusted her with, to make her daughter unforgettable. As Ben Hania puts it: “To honour her voice and make it echo.” Hind’s insistent cries for someone, anyone, to “come to get me” can never now be silenced. They summon up the unfathomable cruelty of Israel’s campaign in Gaza, and the collective failure of the rest of the world to stop the killing.

Ben Hania, who is speaking to me during a recent visit to London, has situated the film somewhere in the borderland between drama and documentary where she has made her career. Her film studies thesis at the Sorbonne University in Paris explored that frontier. Her first film, Challatt Tunes (The Blade of Tunis), was a mockumentary about sexism and violence against women in Tunisia, and her later works have ranged from dramas loosely based on true stories to an intimate documentary about a young Tunisian girl exiled in Canada. “The frontier between the genres is something like the frontier between countries,” she says. “When you are walking, you don’t realise when you’ve entered another country.”

Ben Hania’s film Four Daughters, which she was promoting in early 2024 when she heard Hind’s voice, is about a Tunisian mother called Olfa Hamrouni who has four girls, two of whom have embraced radical Islam and left to join Islamic State. The film plays with the conventions of documentary and drama, intertwining them, so that the real Hamrouni and her two remaining daughters meet the actors who portray them as well the missing girls. The real family comment throughout on their emotions as they watch their drama unfurled before them.

“Since I’m drawn to real stories, I always ask myself what is the best form to tell the story,” the 48-year-old says. “Film-making is about making choices – where to tell the story, how to tell it, in which way, in which form. And to make those choices, I always try to stay faithful to the first moment I encountered the story – what I felt. Because cinema is about emotion.”

During the process of making The Voice of Hind Rajab, she kept going back to the first time she heard that voice and what she felt. “This sense of helplessness. I thought, ‘If I am feeling this, what was it like for the real people who were listening?’ What they felt is a condensation of what we are feeling – so many of us around the world – about what is happening in Gaza. This sense of helplessness. Nobody can reach her to help.”

The film acutely conveys the torment of the two men and two women who are in the emergency call centre. They know there is an ambulance in Gaza City just a few minutes away from Hind and ready to go. But the PRCS has to formally request, through intermediaries, the Israeli army’s permission to approach the area. That permission does not come for hours, as the wounded girl audibly begins to fade.

Send the ambulance anyway, the younger man in the call centre demands, at the end of his tether. But his boss has seen too many ambulance workers die. Their pictures are up on his wall and he has pledged to resign if any more are killed on his watch. In the end, the green light finally comes, but Hind cannot be saved.

Even though the audience knows how the story ends, it is still heartbreaking. It is easier to look away than to witness the killing of a child in harrowing detail. Ben Hania feared her film could simply fade into obscurity, a subtitled Arabic tale of something too hard to face. But at a critical moment, a group of Hollywood stars – including Brad Pitt, Joaquin Phoenix and Rooney Mara, together with directors Alfonso Cuarón and Jonathan Glazer – stepped in to back the project as executive producers.

The film was picked by the Venice film festival where it premiered in September, receiving a 23-minute standing ovation, the longest in the festival’s history. It could have gone on longer, but the cinema had to be cleared so the next movie could be shown. It was only at that moment that Ben Hania realised she had managed to pierce, however fleetingly, the global impassivity that has surrounded two years of slaughter in Gaza.

“So many children have been killed that we are entering a zone of amnesia and insensitivity,” she says. “We’re numb, but cinema, literature and art can change things. At some point, you are done explaining. It is now about feeling what it is like to be in someone else’s shoes. That is another level – and cinema can do this.”

• The Voice of Hind Rajab is released in the UK on 16 January