The photojournalist Tom Stoddart took the shots, one of which depicts a sick child in an ambulance with soldiers outside, with the line, "I was really sick. I could have died. I survived because the soldiers let the ambulance through the checkpoint first."
Other posters show a pregnant woman in a military hospital, a soldier who lost his leg in a land mine explosion, and a man with a fractured skull receiving medical help in the middle of a riot.
Stoddart works with the Getty Images division Reportage, which represents photojournalists around the world, often focusing on conflict.
The photos were staged in a safe environment to recreate scenes Stoddart and other photographers have witnessed.
They are part of the Red Cross "healthcare in danger" campaign to urge people to respect healthcare and health workers in wars, by allowing them to access equipment and people who are injured.
They are appearing on billboards and train carriages in London from today, and in Warsaw, Brussels, Berlin, Amsterdam, Paris and Madrid over the next few weeks.
Olga Miltcheva, a communication officer for the ICRC, said the charity didn’t want to "just do staged photos", but to "bring back the memory of this very tragic reality and the possibility of this change".
The art director was Anthony Holland Parkin from Getty Images, alongside the ICRC, and the producers were Pamela Nolan from Getty Images and the freelance producer Sasha Rickerd.
The ICRC did media planning and buying for the campaign in-house.