Clusters of the campaign's fake accounts were run from different parts of China, but shared digital infrastructure and appeared to operate with clear shift patterns, including breaks for lunch and dinner on Beijing time, Meta said.
China's foreign ministry said it was not aware of the findings, but added that individuals and institutions have often launched campaigns against China on social media platforms.
"We hope that the relevant company adheres to the principle of objectivity and impartiality, and avoids double standards. Truly identify what lies and rumours are, what is the truth, and effectively eliminate false information related to China," foreign ministry spokesperson Wang Wenbin said when asked about the matter at a news briefing on Wednesday.
The "Spamouflage" network first started out posting on large platforms like Facebook, YouTube and Twitter, now called X. More recent activity showed it had expanded its footprint to include smaller platforms like Medium, Reddit, Quora and Vimeo as well, the company said.
It amassed a following of about 560,000 accounts for its pages on Facebook, but Meta executives said they believed most of the accounts were fakes that had been purchased from commercial spam operators in places like Vietnam and Bangladesh.
They said they saw little evidence of genuine audience or engagement beyond that.
"This operation was large and noisy, but it struggled to reach beyond its own fake echo chamber," said Meta's Global Threat Intelligence Lead Ben Nimmo.
In one case suggestive of the accounts' spammy background, a Facebook page that had previously published Chinese-language ads about lingerie abruptly switched to writing English-language posts about riots in Kazakhstan, Nimmo said.