"This includes, but is not limited to, threatening or promoting terrorism", the rule continues.
Fransen and her group Britain First attained global attention when U.S. President Donald Trump retweeted a series of anti-Islamic and inflammatory videos she posted last month. The company also now bans accounts affiliated with "organizations that use or promote violence against civilians to further their causes".
Twitter suspended the accounts of well-known white nationalists Monday, moving swiftly to enforce its new rules aimed at reducing what it deems abusive content. The Traditionalist Worker Party, a group in part founded by neo-Nazi Tony Hovater got banned, as did End Time Paradigm, an anti-Semitic account.
League of the South's Hunter Wallace, Britain First's main account, as well as its leaders Paul Golding and Jayda Fransen-whose anti-Muslim videos were retweeted by President Donald Trump-were also suspended.
Twitter's actions drew praise from civil rights groups.
Hateful imagery will now be considered sensitive media under our media policy.
The step is one of several that Twitter said it would take to crack down on white nationalists and other violent or hateful groups.
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The white nationalist Richard Spencer, whose account was not suspended, tweeted that he had lost more than a hundred followers in the past 24 hours and noted that he didn't "see any systematic method to the #TwitterPurge".
Susan Benesch - a member of Twitter's Trust & Safety Council who serves as executive director of the Dangerous Speech Project and is a faculty associate at Harvard University's Berkman Klein Center for Internet & Society - told Mashable on Monday that Twitter's new rules could be a "slippery slope".
The social media company announced Monday that policy changes the company proposed last month would officially begin taking effect.
Twitter has been overhauling many of its policies in recent weeks following repeated criticism over how it handles abusive content.
It coincides with the platform enforcing new rules and guidelines created to make Twitter a "safer environment".
In a statement, the social site said: "Today, we are starting to enforce these policies across Twitter".
"In our efforts to be more aggressive here, we may make some mistakes and are working on a robust appeals process", it said.