In the 1980s, as a field French doctor working in Afghanistan, I wrote several articles and open letters to the Soviet Union president to avoid the destruction of the Médecins Sans Frontières Wardak hospital. Of course, the Russian planes bombarded it as an answer.

Targeting a red cross drawn on the roof of a hospital is an unacceptable, cowardly and sadly too-frequent accident. And in Kunduz, last week, a line has again been crossed.

In the Médecins Sans Frontières hospital, 12 brave and devoted medics and 10 patients died after a US air bombing. This crime is the symbol of our – the democratic world – common defeat. It was carried out, and in fact authorised, by the end of a long and agonisingly useless war.

The world demands answers. Who were they targeting and why? Under which military orders? This deliberate killing is not acceptable. What took place is a violation of basic human rights. It was committed against humanitarian and international law, in complete contradiction of the Geneva conventions.

It’s a war crime.

13 year-old Nooruddin, a survivor of the US airstrikes on a Médecins Sans Frontières (MSF) Hospital in Kunduz, receives treatment in Kabul. Photograph: Wakil Kohsar/AFP/Getty Images

The entire chain of command is guilty – to bomb a hospital denotes a low opinion of humanitarian help on its part, in spite of the fact that medical volunteers have been working to tend to the wounded and the dying since 1981 without distinction of religion or political involvement.

Humanitarian medical staff who work tirelessly to help patients put their life at risk in doing so. Those who live so far from their homes to tend to wounded patients all over the world are particularly aware of the dangers and risks they undertake – especially in war time. Glory should go to them in the name of fraternity and human kindness.

I pay respect to our humanitarian fighters who enter battle, with conviction, for the remains of human dignity. They were the salt of the earth and should be remembered as such.

And thank you, president Obama, for your call and your devotion to the “French doctors”. But it is not enough to excuse such an unforgivable mistake.

We want an independent investigation.