Meta said on Tuesday it disrupted the first known China-based propaganda operation focused on users in the US, before the midterm elections in November.
The network maintained fake accounts across Meta's social media platforms Facebook and Instagram, as well as competitor service Twitter.
But it was small and did not attract much of a following, Meta said in a report.
The report, however, said the discovery was significant because it suggested a shift towards more direct interference in US domestic politics, compared with previously known Chinese propaganda.
"The Chinese operations we've taken down before talked primarily about America to the world, primarily in South Asia, not to Americans about themselves," Meta global threat intelligence head Ben Nimmo said.
"Essentially the message was 'America bad, China good'."
But Mr Nimmo said the new operation pushed messages aimed at Americans on both sides of divisive issues such as abortion and gun rights.
Another Meta executive said the company did not have enough evidence to say who in China was behind the activity.
US Attorney General Merrick Garland said his office was "very concerned" about intelligence reports of election interference by foreign governments "starting back some time ago and continuing all the way into the present".
A Twitter representative said the company was aware of the information in Meta's report and also took down the accounts.
Meta's report said the Chinese fake accounts posed as liberal and conservative Americans in different states.
They posted political memes and lurked in the comments of public figures' posts since November 2021.
A sample screenshot showed one account commenting on a Facebook post by Republican Senator Marco Rubio, asking him to stop gun violence.
Meta also said it had intercepted the largest and most complex Russian-based operation since the war in Ukraine began.
It described the operation as a sprawling network of more than 60 websites impersonating legitimate news organisations, along with about 4,000 social media accounts and petitions on sites such as US-based campaign group Avaaz.
That operation mainly focused on users in Germany, as well as France, Italy, Ukraine and the UK, and spent more than $100,000 on ads promoting pro-Russian messages.
On a few occasions, Russian embassies in Europe and Asia amplified the content.
