Japan for the first time confirmed the existence of a secret World War II Imperial Army unit accused of using 3,000 people - some of them American prisoners of war - as human guinea pigs in chemical and biological tests.
''It happened during the most extraordinary wartime condition,'' State Minister Kunio Tanabe told the lower house of Japan's Diet (parliament). ''It's most regrettable from the humanity viewpoint.''
The victims were mostly Chinese, Koreans, Mongolians, and Russians, war records show, but some reports say a small number of American POWs also died in the tests.
A best-selling book in Japan says US officials chose not to try the unit's officers for war crimes in exchange for documents and information. CBS's ''60 Minutes'' reported US officials knew at the time about the experiments on US prisoners but did not bring charges for fear the Soviets would copy Japan's ''bacteria bomb.''