Twitter flags 'president-elect Biden' posts as premature
Joe Biden by Gage Skidmore/Flickr

Twitter on Friday flagged as premature posts referring to Joe Biden as "president-elect," as the vote count continued in the knife-edge US election with the Democrat leading Donald Trump in several key states.

Tweets referring to the former vice president with the victor's title and his running mate Kamala Harris as "vice president-elect" were tagged with messages saying counts were not yet final.

"Official sources may not have called the race when this was tweeted," read a message below a post from Democratic Coalition co-founder and podcaster Scott Dworkin using the two titles for Biden and Harris.

The notice came with a link to information about the status of the election.

Twitter and Facebook have been scrambling to flag, mask and limit the spread of premature claims of victory or false attacks on the voting process since the polls closed late Tuesday.

"As votes are still being counted across the country, our teams continue to take enforcement action on tweets that prematurely declare victory or contain misleading information about the election broadly," Twitter said.

"This is in line with our civic integrity policy and our recent guidance on labeling election results."

Unfounded claims by Trump regarding the voting process as well as premature claims of victory about either candidate in the race have been flagged or masked, with links provided to reliable sources of information.

Twitter's action made the comments less visible, and users seeking to read the posts were required to click through a warning.