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".
Israel said it carried out a warning strike against an extremist group that was preparing to attack Druze in Syria, following through on its pledge to protect the minority group as violence spread in Druze areas near Damascus on Wednesday.
Swarms of Russian drones attacked the Ukrainian cities of Kharkiv and Dnipro late on Tuesday, killing at least one person and injuring at least 46, officials said.
At least 14 people died in the eastern Indian city of Kolkata late on Tuesday when a fire blazed through a six-storey hotel in a congested neighbourhood, authorities said.
Spain and Portugal switched their power back on after the worst blackout in their history, though authorities offered little explanation for what had caused it or how they would prevent it from happening again.
The head of Israel's domestic intelligence agency, Ronen Bar, announced he will resign on June 15 amid pressure from Prime Minister Netanyahu and ongoing legal proceedings.
President Donald Trump touted what he called a series of major economic wins and forcefully attacked Democrats during a rally in Michigan on Tuesday to commemorate his first 100 days in office.
Canadian Prime Minister Mark Carney's Liberals retained power in the country's election on Monday, but fell short of the majority government he had wanted to help him negotiate tariffs with US President Donald Trump.