SAN FRANCISCO (BLOOMBERG) - Facebook will "much more aggressively" label posts meant to manipulate or mislead United States voters in the lead-up to November's presidential election, said Mr Nick Clegg, a top company official.

"We're now going to do this much more forcefully between now and November the third," Mr Clegg, Facebook's vice-president for global affairs and communications, said on Sunday (Sept 6) on CNN's Reliable Sources.

Facebook's stepped-up efforts at content-flagging are being done in conjunction with the Washington-based Bipartisan Policy Centre.

The social network last week announced new policies to combat misinformation and voter suppression, including a ban on new political ads on its platform in the week before Election Day, and removal of posts that claim people will contract Covid-19 if they take part in voting.

In a year when increased vote by mail could delay the final results of some contests, the company also said it will add labels to posts from politicians who try to claim victory before official outcomes are known.

Facebook chief executive Mark Zuckerberg has warned of potential "civil unrest and violence" while election results hang in the balance.

Hours after unveiling the changes last week, Facebook flagged a post from President Donald Trump suggesting that people vote in person as well as by mail, which is illegal, adding a label that directed users to its voting information centre.

"Voting by mail has a long history of trustworthiness in the US and the same is predicted this year," Facebook wrote on the label appended to the president's post.

Facebook has been criticised about misinformation that flowed freely on the social-media platform during the 2016 election, and also for not moving quickly enough in the current voting cycle.

"We're moving with the pace of the election campaign," Mr Clegg said. "This is not the first time we've announced policies on election campaigns and how they play out on our platform. We're constantly iterating."