Donald Trump has threatened to “close down” social media platforms after claiming they are biased against conservatives.
On Tuesday, the US president had two tweets from his account flagged with a fact-check warning for the first time after he called US postal voting “fraudulent”.
Under the tweets, there is now a link which reads “Get the facts about mail-in ballots” and guides users to a Twitter page with fact checks and news stories about Mr Trump’s unsubstantiated claims.
In response, Mr Trump accused social media sites of trying to prevent him from winning the 2016 US presidential election and told them to “clean up your act”.
“Republicans feel that Social Media Platforms totally silence conservatives voices,” he wrote.
“We will strongly regulate, or close them down, before we can ever allow this to happen. We saw what they attempted to do, and failed, in 2016. We can’t let a more sophisticated version of that happen again.”
The US president has previously claimed on several occasions, without evidence, that social media platforms are biased against conservatives.
In his latest tweets, Mr Trump also reiterated his claims about postal voting.
“Just like we can’t let large scale Mail-In Ballots take root in our Country. It would be a free for all on cheating, forgery and the theft of Ballots. Whoever cheated the most would win. Likewise, Social Media. Clean up your act, NOW!!!!,” he said.
Twitter has previously been criticised for not taking action against Mr Trump’s account over a number of tweets which appeared to breach the platform’s rules, including spreading misinformation or aiming abuse at individuals.
The firm has generally exempted political leaders from some of its rules, arguing that publishing controversial tweets from politicians encourages discussion and helps hold leaders accountable.
However, it did update its policies last year, confirming it would add warning labels to tweets from politicians which it found to breach the site’s rules.
The social media platform is also under pressure to take action against another set of recent Trump tweets, which repeated a debunked conspiracy theory that Lori Kaye Klausutis, a woman who died in the Florida office of former Republican congressman Joe Scarborough, was murdered by him.
Her widower Timothy Klausutis wrote to Twitter boss Jack Dorsey last week asking him to “please delete these tweets” and said Mr Trump’s promotion of the conspiracy theory around his wife’s death was “bile and misinformation”.
Mr Trump has repeatedly tried to implicate Mr Scarborough in the death even though he was in Washington, not Florida, at the time.
Medical officials ruled Mrs Klausutis, who had a heart condition and told friends hours earlier that she was not feeling well, had fainted and hit her head.
Mr Scarborough, now a US TV host, has publicly feuded with the president in the past and as a result has been a regular target of the US president on social media.
Twitter said it was “deeply sorry about the pain these statements, and the attention they are drawing, are causing the family”, but did not say if it would take action against Mr Trump’s tweets.