Ukrainian director Sergei Loznitsa returns to Cannes Thursday with "The Invasion", a documentary that captures the absurdity of war two years after Russian troops invaded his home country.

"I wanted to show how war transforms a country, a society," the 59-year-old Cannes veteran told AFP.

"War is always absurd. It is madness by definition. A psychiatric disease." 

Through a series of vignettes, the film —  screening out of competition —  examines how this seeps into everyday life.

At the supermarket, two soldiers chat about how much they earn, just like two colleagues at an office coffee machine.

At the town hall, a couple queues to get hitched, one in a white gown and the other in a khaki military uniform.

Conceived as a series of urgent dispatches to convey "a tapestry of life" in the war-torn country, Loznitsa started working on it from the early days of the February 2022 invasion as a question of "duty", though he wanted to avoid propaganda.

Loznitsa was kicked out of the Ukrainian Film Academy in 2022 after criticising its boycott of all Russian films in response to the invasion, a position he still defends.

He is based abroad and had to send a small team into the country to film. 

In one scene, the camera captures piles of books by Russian literary greats Fyodor Dostoevsky and Leo Tolstoy rolling past on a conveyor belt towards a shredder.

"It's a very painful scene for me," said the Ukrainian artist with Belarusian roots who spends his time between Germany, Lithuania and the Netherlands.

"I know the shop, I know the books, I had them on my bedside table during my childhood," he said.

Loznitsa has made fiction films and documentaries since swapping applied mathematics for filmmaking in the 1990s.

He was the first Ukrainian filmmaker to walk the Cannes red carpet when his feature debut "My Joy" screened in the main competition in 2010.

His second feature film "In The Fog" also competed two years later, as did "A Gentle Creature" in 2017.

He screened "Maidan", a documentary about Kiev's pro-EU revolution, in Cannes in 2014.

For "The Invasion", Loznitsa says he instructed his small team —  a cameraman, camera assistant and a sound recordist —  to simply observe and keep the camera rolling.

The result is a film devoid of any interviews, voice-overs or music.

"I don't like to interfere with my material. I don't want to corrupt it with anything," he explained.

"That way... the spectator becomes part of the tragedy."