People attend a memorial ceremony at the Exhibition Hall of Evidences of Crime Committed by Unit 731 of the Japanese Imperial Army in Harbin, northeast China's Heilongjiang Province, Dec. 13, 2016. A memorial ceremony was held at the site of the former Army Unit 731, the Japanese army's biological and chemical warfare unit, on China's National Memorial Day for Nanjing Massacre Victims on Tuesday. (Xinhua/Wang Jianwei)
