The documents, handwritten by Japanese tried and convicted by military courts in China after the war, are being released online one a day for 45 days by the State Archives Administration (SAA), it said in a statement on its website.
In the first, dated 1954 and 38 pages long, Keiku Suzuki, described as a lieutenant general and commander of Japan's 117th Division, admitted ordering a Colonel Taisuke to "burn down the houses of about 800 households and slaughter 1,000 Chinese peasants in a mop-up operation" in the Tangshan area, according to the official translation.
He also "ordered the Epidemic Prevention and Water Supply Squad to spread cholera virus in three or four villages".
The document, which is littered with descriptions of "Japanese imperialists", appeared to have been written by someone with native-level command of Japanese, said one Japanese journalist who saw it.
However, some of the sentences were very long and contained multiple clauses, possibly indicating it had gone through several drafts.
Suzuki was held by Soviet forces at the end of the conflict and transferred to Chinese custody in 1950, earlier Chinese documents said, adding that he was sentenced to 20 years in prison by the court and released in 1963.
The publication of the confessions comes as Tokyo and Beijing are at odds over a territorial dispute in the East China Sea, and as Beijing has argued that a reinterpretation of Japan's pacifist constitution could open the door to re-militarisation of a country it considers insufficiently penitent for its actions in World War II.
Historians concur that Japan was guilty of numerous atrocities in China, including the Nanjing Massacre in 1937 and germ warfare and other experiments conducted by the infamous Unit 731 on live Chinese captives.
