Tokyo and Washington continue to keep under wraps what happened in the Japanese army's research laboratories in Manchuria during the war, an American historian studying Japan's biological warfare said, noting that in this sense, the atrocities linger on more than half a century later.

Referring to the notorious Unit 731's alleged experiments on live prisoners, Sheldon Harris, a professor at California State University, said, "Two generations of Japanese citizens have grown up totally ignorant of these events.

"We in the United States are also guilty of not teaching our young people about what happened (during Japan's war with China)," he said at a gathering at the Bar Association Building in Tokyo Monday.