Facebook on Wednesday banned ads on its flagship website and Instagram that claim widespread voting fraud, suggest US election results would be invalid, or which attack any method of voting.
The company announced the new rules in a blog post, adding to earlier restrictions on premature claims of election victory.
The move came a day after US President Donald Trump used the first televised debate with Democratic challenger Joe Biden to amplify his baseless claims that the November 3 presidential election will be "rigged".
Trump has been especially critical of mail-in ballots, and he cited a number of small unrelated incidents to argue that fraud was already happening at scale.
Facebook has been under fire for refusing to fact-check political ads more broadly and for rampant organic misinformation.
Citing hate speech rules, it also moved Wednesday to remove Trump campaign ads suggesting that immigrants could be a significant source of coronavirus infections.
Facebook said the new election ad prohibition would include those that "portray voting or census participation as useless/meaningless" or that "delegitimize any lawful method or process of voting or voting tabulation... as illegal, inherently fraudulent or corrupt".
Trump tells Ukraine's Zelenskiy to stop hitting Russian diesel
Rescuers search for 130 people after Indonesia passenger ship sinks; six dead
Russia hits passenger train on Ukraine's border with Poland, just misses 'diplomatic train'
Russian drone attack injures five in Ukraine's Odesa, officials say
Philippine ferry fire victims may take months to identify, authorities say
