This decision does not apply to any other advertisers. Political ads will be required to identify their campaigns and will be indicated on Twitter with a different look and feel, the company said in a statement Tuesday.
RT has thrived on social media, particularly YouTube and Facebook.
January's United States intelligence report from the CIA, FBI and NSA included a heavy focus on the alleged role of the two Russian media outlets during the election campaign.
"Twitter's decision should prevent these entities from pushing Russian propaganda in front of users who may not realize the manner in which Russia employs both RT and Sputnik to spread disinformation and undermine democracies around the world", Schiff said in a statement.
The Office of the Director of National Intelligence referred to RT and Sputnik specifically in a report in January as organizations that "contributed to the influence campaign by serving as a platform for Kremlin messaging to Russian and worldwide audiences".
The decision marks one of the most aggressive moves by an American social media company against the Russian outlets, which United States intelligence officials have linked to a wide-ranging Kremlin effort, both covert and overt, to disrupt the 2016 presidential election.More news: Twitter slightly beats on earnings, grows daily users by 14%
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RT also alleged that Twitter had encouraged it to buy advertising in order to expand its reach in the US.
RT, an English-language news channel, accused Twitter's sales staff of pressuring it to spend big on advertising in 2016 ahead of the election.
Twitter said it would disclose who had paid for the election ad and allow users to find information about the buyer, including ad spending history and ad targeting practices. Twitter has since taken some steps toward transparency, announcing earlier this week that it would make all advertising public.
We're donating all projected earnings ($1.9mm) to support external research into the use of Twitter in elections, including use of malicious automation and misinformation.
A USA lawmaker, Representative Adam Schiff, applauded Twitter's move.