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 company said Monday it would begin putting a warning in front of pictures that show Nazi swastikas and other items it determines are hateful imagery, as well as ban their use in any profile photos on the social media network.

The step is one of several that Twitter said it would take to crack down on violent or hateful groups, which have become unwelcome on a service that once took an absolutist view of free speech.

The account of far-right group Britain First, a small group that regularly posts inflammatory videos purporting to show Muslims engaged in acts of violence, was among the first to go dark. The individual accounts of two of its leaders, Jayda Fransen and Paul Golding, were also suspended.

President Donald Trump caused a stir last month when he retweeted a post by Fransen, drawing criticism from British Prime Minister Theresa May. Fransen and Golding were arrested in Belfast last week for allegedly stirring up hatred.

Twitter said it will weigh hateful imagery in the same way it does graphic violence and adult content on its site. That means users may not use such imagery in live video or profile and header images.

The company has emphasized that it takes into account many factors before making any enforcement decision, including context of the post, cultural and political considerations and the severity of the violation.

Twitter's actions drew praise from civil rights groups.

Jonathan Greenblatt, CEO of the Anti-Defamation League, commended Twitter "for taking these significant steps to tackle hate on their platform." The group Muslim Advocates, which had publicly called for the removal of Britain First's account, applauded Twitter for "updating its policies and taking steps today to remove violent and hateful accounts from its platform."

Twitter, a San Francisco company founded in 2006, had called itself "the free speech wing of the free speech party" and tried to stay out of battles among users. But that has changed as persistent harassers have driven some women and minorities off Twitter, limiting their ability to express themselves.

A rise in white nationalism in the United States has also changed tech industry standards. In August, social media networks began removing white nationalists after hundreds gathered in Charlottesville, Virginia, and one of them was charged with murdering a 32-year-old woman by running her down in a car.

In October, Twitter vowed to toughen rules on online sexual harassment, bullying and other forms of misconduct.

Tweets can still include hate imagery, but users will have to click through a warning to see them, the company said. Hate images will be banned from profile photos, and further restricted where national laws require, as in Germany.

The Nazi swastika was the only specific example of a hateful image that Twitter gave, but the company said it would try to give warnings for all symbols historically associated with hate groups or which depict people as less than human.

Twitter said it had decided not to categorize the U.S. Confederate flag as hateful imagery, citing its place in history.

The account for Jared Taylor, who heads the New Century Foundation, was among those suspended, along with his organization's flagship online publication, American Renaissance.

Taylor said he immediately appealed the suspension but swiftly received a reply from Twitter informing him that his account would not be restored, which he interpreted to mean he had been permanently banned.

He said Twitter determined his account was "affiliated with a violent extremist group," an allegation he denied.

"Of all the preposterous things they could have said about me or American Renaissance, I can't think of anything more preposterous," Taylor said.

New Century Foundation has been recognized as charity by the IRS, a decision that has drawn criticism from civil rights advocates. Taylor has said his group raises money for the benefit of the "white race."

Brad Griffin, who blogs under the name Hunter Wallace on the website Occidental Dissent, said in blog post that he was also suspended, along with Michael Hill, president of the League of the South, the Traditionalist Workers Party and others. American Renaissance and Occidental Dissent both referred readers to an online chat site frequented by white nationalists.

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."

There appeared to be some inconsistencies. Twitter allowed David Duke to keep the message "It's Ok To Be White" as his header, even though the same phrase was hidden by the "sensitive material" warning on his pinned tweet.

Emma Llanso, director of the free expression project at the Center for Democracy and Technology, said the new guidelines represent a substantial change for Twitter's policies. But, he added, it's not going to be immediately clear to all users what falls within the new prohibitions.

"It's essential that they provide clarity to the users whose content is removed," said Llanso, whose nonprofit is a member of the Trust and Safety Council group of outside organizations advising Twitter.

"In our efforts to be more aggressive here, we may make some mistakes and are working on a robust appeals process," Twitter said in a blog post Monday.