Hours after a video purportedly showing the brutal beheading of American journalist James Foley started circulating online, Twitter announced Wednesday that it is "actively" suspending accounts that share the gory images.

As journalists and others rushed to self-censor and stop the spread of the graphic imagery, Twitter was ramping up its effort to avoid becoming an indirect propaganda channel for the group claiming responsibility for Foley's murder, the Islamic State (formerly known as ISIL or ISIS.)

Twitter CEO Dick Costolo announced the move:

We have been and are actively suspending accounts as we discover them related to this graphic imagery. Thank you https://t.co/jaYQBKVbBF — dick costolo (@dickc) August 20, 2014

Many Islamic State fighters, or supporters claiming to be fighters, often share violent pictures and propaganda on Twitter. And American spy agencies might actually be happy to let them use the network, since it helps them gather intelligence, as Mashable revealed last month.

But now, some accounts related to the Islamic State seem to be getting shut down at a faster rate.

Pieter Van Ostaeyen, a researcher who's been tracking Islamic State fighters and supporters on the Internet for months, started noticing the suspensions soon after the news of the beheading started spreading online.

If it goes on at this rate ... #IS twitter accounts are being taken down in the dozens #socialmedia vs. #IS — Pieter Van Ostaeyen (@p_vanostaeyen) August 19, 2014

Then on Wednesday, Van Ostaeyen noticed that many accounts he was following, allegedly belonging to Islamic State fighters, had been suspended overnight.

This says it all ... pic.twitter.com/mZu2fYAGfZ — Pieter Van Ostaeyen (@p_vanostaeyen) August 20, 2014

Islamic State fighters and supporters also took notice, inviting others to avoid suspension by deactivating their accounts or periodically changing handles.

Looks like pro-ISIS accounts may be deactivating their accounts on purpose to avoid bans h/t @ArtWendeley pic.twitter.com/q00YnqPcKW — Brown Moses (@Brown_Moses) August 19, 2014

Quite a few IS accounts changing their handles periodically in an attempt to avoid being suspended. — J.M. Berger (@intelwire) August 19, 2014

At least one Islamic State account was apparently suspended and then reactivated.

"Please let me know if I can help with anything else." pic.twitter.com/kxEFZ4ddvc — J.M. Berger (@intelwire) August 20, 2014

Twitter has traditionally erred on the side of freedom of speech when it comes to policing content. It has suspended accounts only when they break any of its content rules, which include a prohibition against posting "direct, specific threats of violence against others."

In any case, suspensions normally depend on other users reporting the abusive behavior.

It's unclear which company policies, if any, are prompting this new wave of suspensions. It could be those related to threats, since the beheading video ended with a threat to kill another imprisoned American journalist, Steven Joel Sotloff. Or, perhaps, Twitter is applying its new rules on the removal of imagery of deceased people, which the company published on Tuesday evening.

(The timing of the new policy may have been coincidental and possibly related to harassment of Robin Williams' daughter after the actor's death last week. Twitter did not respond to Mashable's multiple requests for comment.)

Some Twitter users are confused by these suspensions as well. Some, for example, are wondering whether Twitter should suspend the account of the New York Post for tweeting a picture of its Wednesday cover, which shows an image of Foley just instants before his death.

Twitter says it is "actively suspending accounts" posting James Foley beheading images. Will it suspend @nypost? http://t.co/KXDRcyaKeo — Neetzan Zimmerman (@neetzan) August 20, 2014

Others asked Twitter to suspend the Post's Twitter account.

just reported @nypost for a photo of the act of beheading. You should to. If @twitter suspends a reg users acct, @nypost should be too. — Fenrir (@semibogan) August 20, 2014

But a Twitter spokesperson told Business Insider that the Post's account would not be suspended (nor that of the Daily News, which tweeted a somewhat less graphic image).

Twitter is walking a fine line here, and given the gravity of the issue, whatever it does it's probably bound to be controversial.

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