In China, even a child can tell you horrifying stories of the No. 731 unit of the invading Japanese troops who in one case killed more than 3,000 Chinese through "bacteriological experiments" during World War II.

This is merely the tip of the iceberg, however, as an in-depth study by Chinese and Japanese scholars shows that at least 270,000 Chinese soldiers and civilians were slaughtered by Japanese germ- warfare troops between 1933 and 1945.

Chinese scholars, including Guo Chengzhou and Liao Yingchang from the Academy of Medical Sciences attached to the Chinese People's Liberation Army (PLA), put the figure at more than 270, 000, but some Japanese experts believe the total is no less than the number of people killed in the Nanjing Massacre, in which at least 300,000 Chinese died.

Though differing on the number of victims, both Chinese and Japanese researchers agree that the germ-war waged by invading Japanese army was on the largest scale the world has ever seen in terms of duration, casualties, and impact.

The researchers have spent years seeking evidence from the libraries and archives of the international courts that handled the cases of Japanese war criminals, and interviewed victims of the Japanese troops' bacterial operations and their relatives, as well as former Japanese soldiers who participated in this atrocity.

Many articles and books have been published and a dozen seminars and four international conferences have been held on this issue. A group of Japanese investigators has visited China four times to study this "bacteriological experiment war."

According to the researchers, Japanese troops who invaded China between 1932 and 1945 set up a germ-warfare base in Wuchang County in northeast China's Heilongjiang Province in 1933 and eventually deployed five "bacteriological experimentation units" with a total of over 20,000 men in the cities of Harbin, Changchun, Beijing, Nanjing and Guangzhou.

A report delivered at a secret meeting held at the headquarters of the invading Japanese troops in 1943 discloses that the " bacteriological experimentation units" turned out 75 kilograms of bacteria a month.

During the war, 20 Chinese provinces were attacked by these Japanese units who spread deadly diseases including typhoid, cholera, diarrhea fever, anthrax, lockjaw and gangrene.

Wang Laiyong, 64, is one of five victims from Yiwu in east China's Zhejiang Province who survived the "bacteriological experiment" conducted by Japanese troops in October 1942.

Japanese aircraft arrived and sprayed something like a white fog in the air above Wang's village. Shortly afterwards, many rats were found dead, followed by many villagers who fell ill, vomiting foam and blood. This lethal operation killed 386 villagers, according to official statistics.

The Chinese survivors and victims' relatives as well as many Japanese soldiers now remember this germ-warfare as a nightmare.

Some members of the "Japanese experimentation units" have helped investigators collect evidence and find witnesses to these deadly operations that caused such wide-spread epidemic diseases and killed so many people.

Some former Japanese soldiers who were involved in these genocidal activities have made special trips to China to offer their apologies for what they did during those unforgettable years.