A slew of documents regarding the Nanjing Massacre were published in both paper and digital versions Monday.

The documents published in Nanjing, capital city of east China's Jiangsu Province, fall into seven compilations totalling over 20 volumes, with narratives in Chinese, and translations in English and Japanese.

They are comprised of the court testimonies of Japanese war criminals, diaries and records of Japanese invaders, written documents of Chinese victims and records written by people from abroad.

In October 2015, the Documents of the Nanjing Massacre was inscribed on the Memory of the World Register by the International Advisory Committee of the UNESCO Memory of the World Programme.

"The published documents will expose to the world one of the darkest moments in human history and reveal what truly happened. The files will be another powerful response to Japanese right-wingers who deny or commit slander regarding this part of history," said Li Minghua, head of the State Archives Administration of China.

Japanese troops captured Nanjing, then China's capital, on Dec. 13, 1937 and started about 40 days of slaughter. About 300,000 civilians and unarmed Chinese soldiers were brutally murdered. Over 20,000 women were raped.

Dec. 13 is a nationwide memorial day for the massacre.