The report published last week claims technicians at African Union (AU) headquarters in the Ethiopian capital discovered last year that the contents of their computers had been regularly copied to servers in Shanghai since 2012, citing several unnamed AU sources.
"I think the report is a sensational story, but is also preposterous and absurd," Chinese envoy Kuang Weilin said on the sidelines of the AU summit in Addis Ababa.
The twice-yearly meeting is taking place in a soaring conference hall built by the Chinese as a symbol of their friendship with Africa and inaugurated the same year the alleged spying began.
Weilin said the report published last week on the eve of the summit "will undermine the image of the newspaper" but not the relationship between China and Africa.
AU commission chairperson Moussa Faki Mahamat played down the allegations during a press conference after the summit's close, saying he had seen "no evidence of espionage in the building," a sentiment shared by at least one African leader.
Le Monde says the AU's servers were changed and its IT systems redone after the copying was found.
The newspaper also reports that Ethiopian cyber security experts removed microphones hidden in the desks and walls of the headquarters.
China is deeply invested in Africa, regularly offering low-interest loans and gifts to individual nations and doing $149.2 billion (120.3 billion euros) in trade with the continent in 2016.