Images of destruction from the Gaza Strip

The first image you see in the German photographer Kai Wiedenhofer's new exhibition is a Palestinian woman staring at the camera, dignified and composed. There are bullet holes in the wall behind her - as one might expect from a collection called The Book of Destruction: Gaza after the 2009 War. It's only when you look closely that the full effects of that war become clear. In the place of her hand is a mangled stump.

Wiedenhofer looks at the image and shakes his head. "Psychologically, this was the most difficult thing I've ever done," he says of a project that took him to Gaza last year. Once there, he recorded the aftermath of the Israeli offensive and its ruinous effects on the inhabitants and buildings. And the results are striking. In one shot, a young woman sits in a comfortable armchair. She's a double amputee and yet she appears to be smiling. There's no anger in these portraits, many of women and children, just an invitation for deep reflection on war's terrible cost to the living as well as the dead.

This celebrated German photographer has been documenting conflict throughout his career. His two previous books, Perfect Peace and Wall, have detailed almost exclusively the effects of conflict on the Palestinian people. He's often been labelled controversial and anti-Israeli: when The Book of Destruction opened in Paris last year, two men tried to break into the building to destroy the exhibits. But Wiedenhofer is unconcerned by such accusations.

"It doesn't bother me one bit, honestly," he says, taking a break from the physical toil of hanging his shots at the Mosaic Rooms - an art space in west London with a brief to deliver a contemporary, progressive cultural programme from the Middle East. "I wanted to make a record, that's all. People can go and talk to these people with amputations if they like. What's become clear since taking these photographs is that we could have made the same book in Iraq or Afghanistan. For me, it's the way war is perceived that is interesting, too. It's not so sophisticated and precise as people think."

Wiedenhofer jumps up from his chair and finds the book that accompanies this exhibition, flicking to a page showing the terrible effects of a misguided drone attack. It's another shot of a broken body, but once again it's the sheer human spirit which shines through. "I really want to get across this idea that when there's a rocket attack - which can be anywhere where there's war - it's essentially a 20-year-old kid sitting with a joystick in a room, directing a drone. He thinks he sees something and that's it. So for example, and this is the background to this photo," he says, jabbing the book, "a soldier can see a guy carrying an oxygen bottle and mistake it for a rocket, send in the drone and kill and injure people. And though we always hear about the dead on the news reports, it's the injured we often forget about."

Such concerns might make Wiedenhofer sound like a photojournalist, but beyond documenting the effects of war, there is an artistic beauty to these images. His pictures are elegant rather than voyeuristic, all the more surprising when Wiedenhofer admits that he's never attempted portraiture before. Even the images of mangled buildings have a strange beauty. In one memorable landscape, a container is torn to pieces. But through the ripped apart metal, the southern Mediterranean shimmers in the background. He might call himself a documentary photographer - "the idea of a photojournalist barely exists any more," he jokes - but there's a definite artistic element to all his work.

"Yes, you could say that," he says. "I shoot what's visually interesting for me. But with these people you don't have to overdramatise, you don't have to use Photoshop or flashy lighting - the state people are in is bad enough. I just wanted them to look straight in the camera."

Wiedenhofer admits that, after his two previous books, he hadn't intended to return to Palestine again. In fact, he looks me straight in the eye when he says that he did so because the Foundation Carmignac Gestion paid him rather well.

His brief may not have been to tell both sides of the story, and there may have been a financial imperative. But what he found when he got to Gaza will, you sense, remain with him for the rest of his life.

"These people have lost their legs, their arms, or they're blind," he winces. "And visiting them a year after their injuries means you're speaking to people who are fully aware of what their predicament will mean for them. People cope differently - some exercise, others overeat and become fat - but it was hard to deal with, for them and me. What you soon realise is that these people need money and help for medical aid - but they don't always get it because, perhaps, someone they know is affiliated with an extremist group. Someone can lose a little finger and get treatment and someone else can lose two legs and nothing happens. It's very complicated."

So one of Wiedenhofer's hopes for the exhibition and book is that the specific people he photographed are helped. Indeed, any funds raised will be directed towards his subjects. But there is a broader aim, too.

"On a more general level, I'd like people to think about war," he says, quietly. "It's not just about the injured person in the photograph, the brother, the mother, the friends, everyone has to help them. These injuries have shock waves way beyond the actual person who is suffering from them."

The Book of Destruction: Gaza - One Year After The 2009 War is at the Mosaic Rooms, London until February 12. The book is published by Steidl/Fondation Carmignac Gestion in June. www.mosaicrooms.org