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".
Russian ballistic missiles killed at least five people and injured over two dozen more in Kyiv early on Thursday, authorities said on the Telegram messaging app, damaging buildings and leaving parts of the Ukrainian capital without power.
South Korea and the United States will cut short annual joint military drills to five days from 11 and scale back some field training, the allies said on Wednesday, after President Donald Trump ordered a substantial reduction in US participation.
At least 100 people were killed when a low-tech artisanal gold mine collapsed in the Central African Republic on Tuesday, a senior official at a local mining association said.
An Israeli airstrike killed nine Palestinians at a police station in Gaza on Wednesday, medics said, two days after US envoy Jared Kushner ended a trip to the region that failed to push forward Donald Trump's plan to end the war in the enclave.