Jin Chengmin, a researcher on germ and gas warfare of Japanese troops, found the evidence in a Tokyo library in 2001.

Jin said the experiments were documented in 1941 as "research results" with about 100,000 words, over 20 photographs and 100 diagrams. The document included descriptions of specific experiments, the names, genders and ages of the subjects, the degree of frostbite and dissections of bodies.

Eight male Chinese, aging from 15 to 49, were victims of the experiments carried out from Jan. 31 to Feb. 11, 1941 in Mongolia.

According to the document, the men were exposed outdoors to temperatures of about 27 degrees Celsius below zero with some being deliberately cut or forced to wear wet shoes.

The document recorded the victim's reactions. For example, one teenager became "furious" four minutes after the experiment began, wailed 30 minutes later and could no longer feel his feet after one and half hours.

The Japanese criminals claimed the experiments were done to learn how to deal with frostbite afflicting Japanese soldiers during the war.

Jin said Japan set up 63 branches in China to develop and manufacture weapons for germ warfare with Japan's Unit 731 as the headquarters during World War II.

Captives from many countries and Chinese civilians were deliberately infected with the plague, cholera and anthrax as well as being exposed to toxic gases.

Before Japan's retreat from China in August 1945, the Unit destroyed most of the incriminating evidence. However the photographs of the frostbite experiments are direct evidence that the Japanese experimented on human beings, Jin said.

Backgrounder: Japanese Wartime Human Experiments in China

Japan's Unit 731, part of Japan's Kwantung Army, is notorious for manufacturing materials for germ warfare and testing them on live people during World War II.

With a research center set up in 1932 in Harbin in northeast China's Heilongjiang Province, Unit 731 appointed over 3,000 medical and other researchers to develop and make weapons for germ warfare.

Captives from many countries and Chinese civilians were deliberately infected with plague, cholera and anthrax and exposed to toxic gases.

Over 10,000 healthy Chinese, Russian, Korean and Mongolian civilians were tortured to death.

Research shows the Unit was capable of producing enough germ warfare weapons to destroy mankind many times.

Before their retreat in August 1945, the Unit destroyed most of the incriminating evidence.

However, some documents were later found and made public by experts.

The frostbite experiments revealed Tuesday were carried out by the Beijing Unit 1855 of the Japanese troops. A former interpreter with the army, who died last year, said that "The army tested at least 500 people every year on average."

Japanese germ warfare experiments have affected the whole world and yet most of the perpetrators escaped trial.

Since 2000 over 300 instruments used in wartime dissections have been discovered at the site of Unit 731, where a theme park is now being constructed.

(Edited from Xinhua News Agency, August 14, 2002)