HARBIN -- Hideo Shimizu, a former member of Unit 731, the notorious Japanese germ-warfare detachment during World War II, identified the crimes of the Japanese army on Tuesday at the site where he served 79 years ago in China.

Shimizu, 94, arrived by plane in the city of Harbin, Northeast China's Heilongjiang province, on Monday evening and visited the former site of Unit 731's headquarters building, including the office of the unit commander, the specimen room, and the site of the frostbite laboratory, here on Tuesday morning.

He recalled that in the specimen room, he had seen a variety of dissected human organs soaked in formalin-filled bottles, and he had been ordered to collect the bones of prisoners who were used as experimental subjects.

Shimizu was among the last batch of Unit 731 Youth Corps members sent by Japan to Harbin, where he spent more than four months witnessing the war crimes committed by the unit, including the cultivation of pathogens, human dissections and human experiments. He fled China with the retreating Japanese forces on August 14, 1945.

In 2016, Shimizu revealed his identity as a former Unit 731 member and began to expose the atrocities of the Japanese Imperial Army through public speeches and interviews, aiming to tell historical truths.

This visit is Shimizu's first return to Chinese soil in 79 years. He had previously expressed a strong desire to return to China to pray for the deceased and apologize to their families. The trip was made possible by donations from various Japanese civilian groups.

"For me, overcoming many difficulties to return to China is about hoping that the Japanese authorities can face history squarely, safeguard peace, and not repeat the mistakes of war," Shimizu said.

Unit 731 was a top-secret biological and chemical warfare research base established in Harbin as the nerve center for Japanese biological warfare in China and Southeast Asia during World War II.

At least 3,000 people were used in human experiments by Unit 731, while more than 300,000 people in China were killed by Japan's biological weapons.