San Francisco, Oct 1 (IANS): After US President Donald Trump attacked the integrity of the upcoming election with false claims about voter fraud and mail-in ballots, Facebook has said it will not allow ads with content that seeks to delegitimise the outcome of an election.

Facebook updated its policies less than 24 hours after Trump, in a debate with the Democratic nominee Joseph R Biden Jr on Tuesday, refused to agree to accept the election outcome.

"Last week we said we'd prohibit ads that make premature declarations of victory. We also won't allow ads with content that seeks to delegitimize the outcome of an election," Facebook Product Manager Rob Leathern said in a tweet on Wednesday.

This would "include calling a method of voting inherently fraudulent or corrupt, or using isolated incidents of voter fraud to delegitimise the result of an election", he added.

The new changes apply to ads across Facebook and Instagram with an immediate effect.

Earlier in September, Facebook CEO Mark Zuckerberg said the company is going to block new political and issue ads during the final week of the campaign.

"It's important that campaigns can run and get out the vote campaigns, and I generally believe the best antidote to bad speech is more speech, but in the final days of an election there may not be enough time to contest new claims," he wrote in a Facebook post.

"So in the week before the election, we won't accept new political or issue ads".

Zuckerberg said they are going to extend the work with election officials to remove misinformation about voting.

"We already committed to partnering with state election authorities to identify and remove false claims about polling conditions in the last 72 hours of the campaign, but given that this election will include large amounts of early voting, we're extending that period to begin now and continue through the election until we have a clear result", the Facebook CEO informed.