Twitter labeled two of US President Donald Trump s tweets with a fact-check label on Tuesday for the first time, prompting the president to accuse the platform of stifling free speech.

The social media platform applied the label on two of Trumps tweets that made claims, without evidence, that voting with mail-in ballots would be substantially fraudulent. The Twitter labels say Get the facts about mail-in ballots and direct users to a collection of news reports and articles debunking the tweets.

Near the top of Twitters fact-check page, a statement reads: Trump falsely claimed that mail-in ballots would lead to a Rigged Election. However, fact-checkers say there is no evidence that mail-in ballots are linked to voter fraud.

The president has ramped up his attacks to discredit the integrity of mail-in voting in recent weeks, despite substantial evidence to the contrary.

Twitter spokesperson Katie Rosborough said the tweets were labeled because they contain potentially misleading information about voting processes and have been labeled to provide additional context around mail-in ballots.