A new set of books have been released in China documenting the Nanjing Massacre.

The books come in three sets, and include 5 volumes each.

They include letters and documents collected from Japanese army officers, as well as accounts from survivors, along with media reports from neutral sources.

Wang Weixing is the director of the Institute of History at the Jiangsu Provincial Academy of Social Sciences.

"The Japanese eyewitness accounts in these books admitted that 40,000 to 50,000 Chinese were killed in the Nanjing Massacre: this casualty count is by far the biggest number we've seen in historical materials from the Japanese side."

Confusion at the time of the Nanjing Massacre, which began in late 1937 during the height of Japan's invasion of China, has created a wide gap in the estimates of the number of people killed, with figures ranging anywhere from 40-thousand to upward of 300-thousand.

The release of the new books comes ahead of the first Nanjing Massacre memorial day to be held here in China on December 13th.