The Imperial Japanese Army collected blood from prisoners of war (POWs) and local Chinese residents for "research on battlefield blood transfusion techniques" during its invasion of China, Kyodo News reported on Thursday.

Kyodo News uncovered the relevant records in a report presented at a 1940 medical conference and published in the journal of the Japanese Army Medical Corps.

According to the report, a Japanese army surgeon was dispatched to northern China after July 1937 and administered serum to individuals requiring blood transfusions to test its therapeutic effectiveness.

Initially, the serum was supplied by air from the Imperial Japanese Army Medical School in Tokyo. Later, however, blood was collected from "comrades, local residents, prisoners of war, bandits and others," making it possible to secure supplies in large quantities.

Kyodo News noted that the term "bandits" was used by Japan at the time to refer to armed groups resisting its rule.

The report also stated that blood loss amounting to 3.3% of a person's body weight was considered the "lethal level of blood loss in human experimentation," although it did not specify the subjects of those experiments.

The report further indicated that army surgeons conducted another experiment related to the fatal level of blood loss. They injected dried blood into 12 test subjects who had lost roughly 3% of their body weight in blood to observe its therapeutic effects and side effects. However, the report did not disclose the identities of the subjects or explain how they had been selected for the experiment.

In recent years, Japanese researchers and media outlets have uncovered additional evidence of wartime atrocities committed by the Japanese military, including human experimentation.

Kyodo News reported on June 20 that a report from a Japanese military medical conference held in March 1940 suggests the Imperial Japanese Army may have repeatedly conducted experiments in China involving the transfusion of animal blood into humans during its invasion.

Some historians have pointed out that Japan should thoroughly reflect on its war of aggression and the atrocities it committed, including human experimentation and other war crimes.